chore(eslint): enable quotes: ["error", "single"]

The quotes rule had to be disabled for e2e tests generated from ngdoc
because dgeni templates use double quotes as string delimiters.

Since we can't have guarantees that dgeni template wrappers will follow
the same JS code style the Angular 1 repo uses, we should find a way
to enforce our ESLint setup only for the parts in this repo, perhaps
via prepending a generated `/* eslint-enable OUR_RULES */` pragma.

Closes #15011

angularFiles.js

@@ -209,7 +209,7 @@ var angularFiles = {
     'build/docs/docs-scenario.js'
   ],
 
-  "karmaModules": [
+  'karmaModules': [
     'build/angular.js',
     '@angularSrcModules',
     'test/modules/no_bootstrap.js',