docs: update CLI strict mode documentation (#39054)

With this change we update the strict mode documentation to reflect the
changes done in the CLI. (https://github.com/angular/angular-cli/pull/18931)

Changes effect
- Removing `no-any` tslint rule
- The special sideEffects  package.json
- Added `strictTemplates` NGC option

PR Close #39054

aio/content/guide/file-structure.md

@@ -95,7 +95,6 @@ Angular components, templates, and styles go here.
 | `app/app.component.css`     | Defines the base CSS stylesheet for the root `AppComponent`. |
 | `app/app.component.spec.ts` | Defines a unit test for the root `AppComponent`. |
 | `app/app.module.ts`         | Defines the root module, named `AppModule`, that tells Angular how to assemble the application. Initially declares only the `AppComponent`. As you add more components to the app, they must be declared here. |
-| `app/package.json`              | This file is generated only in applications created using `--strict` mode. This file is not used by package managers. It is used to tell the tools and bundlers whether the code under this directory is free of non-local [side-effects](guide/strict-mode#side-effect). |
 
 ### Application configuration files
 

aio/content/guide/strict-mode.md

@@ -1,17 +1,15 @@
 # Strict mode
 
-When you create a new workspace or a project you have an option to create them in a strict mode using the `--strict` flag.
+When you create a new workspace or an application you have an option to create them in a strict mode using the `--strict` flag.
 
-Enabling this flag initializes your new workspace or project with a few new settings that improve maintainability, help you catch bugs ahead of time, and allow the CLI to perform advanced optimizations on your application.
+Enabling this flag initializes your new workspace or application with a few new settings that improve maintainability, help you catch bugs ahead of time.
 Additionally, applications that use these stricter settings are easier to statically analyze, which can help the `ng update` command refactor code more safely and precisely when you are updating to future versions of Angular.
 
 Specifically, the `strict` flag does the following:
 
 * Enables [`strict` mode in TypeScript](https://www.staging-typescript.org/tsconfig#strict), as well as other strictness flags recommended by the TypeScript team. Specifically, `forceConsistentCasingInFileNames`, `noImplicitReturns`,  `noFallthroughCasesInSwitch`.
-* Turns on strict Angular compiler flags [`strictTemplates`](guide/angular-compiler-options#stricttemplates) and [`strictInjectionParameters`](guide/angular-compiler-options#strictinjectionparameters)
+* Turns on strict Angular compiler flags [`strictTemplates`](guide/angular-compiler-options#stricttemplates), [`strictInjectionParameters`](guide/angular-compiler-options#strictinjectionparameters) and [`strictTemplates`](guide/angular-compiler-options#stricttemplates).
-* [Bundle size budgets](guide/build#configuring-size-budgets) have been reduced by ~75%
+* [Bundle size budgets](guide/build#configuring-size-budgets) have been reduced by ~75%.
-* Turns on [`no-any` tslint rule](https://palantir.github.io/tslint/rules/no-any/) to prevent declarations of type `any`
-* [Marks your application as side-effect free](https://webpack.js.org/guides/tree-shaking/#mark-the-file-as-side-effect-free) to enable more advanced tree-shaking
 
 You can apply these settings at the workspace and project level.
 
@@ -30,17 +28,3 @@ To create a new application in the strict mode within an existing non-strict wor
 ng generate application [project-name] --strict
 
 </code-example>
-
-{@a side-effect}
-
-### Non-local side effects in applications
-
-When you create projects and workspaces using the `strict` mode, you'll notice an additional `package.json` file, located in `src/app/` directory.
-This file informs tools and bundlers that the code under this directory is free of non-local side effects. Non-local side effects in the application code are not common and using them is not considered a good coding pattern.
-More importantly, code with these types of side effects cannot be optimized, resulting in increased bundle sizes and applications that load more slowly.
-
-If you need more information, the following links may be helpful.
-
-* [Tree-shaking](https://webpack.js.org/guides/tree-shaking/)
-* [Dealing with side effects and pure functions in JavaScript](https://dev.to/vonheikemen/dealing-with-side-effects-and-pure-functions-in-javascript-16mg)
-* [How to deal with dirty side effects in your pure function JavaScript](https://jrsinclair.com/articles/2018/how-to-deal-with-dirty-side-effects-in-your-pure-functional-javascript/)