test(docs-infra): compile only app for examples with no e2e (#33717)

With TS 3.7, these examples were running into the error below (e.g. on https://circleci.com/gh/angular/angular/574906#tests/containers/0):

```
============== AIO example output for: /home/circleci/ng/aio/content/examples/observables/
running: yarn tsc --project ./
$ /home/circleci/ng/aio/content/examples/observables/node_modules/.bin/tsc --project ./
../../../tools/examples/shared/node_modules/protractor/built/index.d.ts(5,10): error TS2440: Import declaration conflicts with local declaration of 'PluginConfig'.
../../../tools/examples/shared/node_modules/protractor/built/index.d.ts(5,24): error TS2440: Import declaration conflicts with local declaration of 'ProtractorPlugin'.
error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
completed: yarn tsc --project ./
```

This happened because of https://github.com/angular/protractor/issues/5348.

It's unclear why this typings problem does not affect `ng e2e` runs, and only affects `tsc` runs.

For now it seems sensible to alter the tests to compile only the app and not the e2e, since the intent of 2cc954d5a5 was never to verify the correctness of the e2e in the first place.

We still need a release of protractor that supports TS 3.7 though, but at least it doesn't seem to block our update proper.

PR Close #33717

aio/content/examples/observables-in-angular/example-config.json

@@ -2,7 +2,7 @@
   "e2e": [
     {
       "cmd": "yarn",
-      "args": [ "tsc", "--project", "./" ]
+      "args": [ "tsc", "--project", "./tsconfig.app.json" ]
     }
   ]
 }

aio/content/examples/observables/example-config.json

@@ -2,7 +2,7 @@
   "e2e": [
     {
       "cmd": "yarn",
-      "args": [ "tsc", "--project", "./" ]
+      "args": [ "tsc", "--project", "./tsconfig.app.json" ]
     }
   ]
 }

aio/content/examples/practical-observable-usage/example-config.json

@@ -2,7 +2,7 @@
   "e2e": [
     {
       "cmd": "yarn",
-      "args": [ "tsc", "--project", "./" ]
+      "args": [ "tsc", "--project", "./tsconfig.app.json" ]
     }
   ]
 }

aio/content/examples/rx-library/example-config.json

@@ -2,7 +2,7 @@
   "e2e": [
     {
       "cmd": "yarn",
-      "args": [ "tsc", "--project", "./" ]
+      "args": [ "tsc", "--project", "./tsconfig.app.json" ]
     }
   ]
 }