style(docs-infra): fix docs examples for tslint rule `jsdoc-format` (#38143)

This commit updates the docs examples to be compatible with the
`jsdoc-format` tslint rule.

This is in preparation of updating the docs examples `tslint.json` to
match the one generated for new Angular CLI apps in a future commit.

PR Close #38143

aio/content/examples/structural-directives/src/app/unless.directive.ts

@@ -1,3 +1,4 @@
+// tslint:disable: jsdoc-format
 // #docplaster
 // #docregion
 // #docregion no-docs, skeleton

aio/content/examples/testing/src/app/shared/highlight.directive.ts

@@ -2,8 +2,10 @@
 import { Directive, ElementRef, Input, OnChanges } from '@angular/core';
 
 @Directive({ selector: '[highlight]' })
-/** Set backgroundColor for the attached element to highlight color
- *  and set the element's customProperty to true */
+/**
+ * Set backgroundColor for the attached element to highlight color
+ * and set the element's customProperty to true
+ */
 export class HighlightDirective implements OnChanges {
 
   defaultColor =  'rgb(211, 211, 211)'; // lightgray

aio/content/examples/testing/src/testing/async-observable-helpers.ts

@@ -13,16 +13,20 @@
 import { defer } from 'rxjs';
 
 // #docregion async-data
-/** Create async observable that emits-once and completes
- *  after a JS engine turn */
+/**
+ * Create async observable that emits-once and completes
+ * after a JS engine turn
+ */
 export function asyncData<T>(data: T) {
   return defer(() => Promise.resolve(data));
 }
 // #enddocregion async-data
 
 // #docregion async-error
-/** Create async observable error that errors
- *  after a JS engine turn */
+/**
+ * Create async observable error that errors
+ * after a JS engine turn
+ */
 export function asyncError<T>(errorObject: any) {
   return defer(() => Promise.reject(errorObject));
 }