Remove index files for easier G3 sync

Author: devversion

src/cdk/index.ts

@@ -46,8 +46,10 @@ System.config({
       'node:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic-testing.umd.js',
 
     // Path mappings for local packages that can be imported inside of tests.
-    '@angular/material': 'dist/packages/material/index.js',
-    '@angular/cdk': 'dist/packages/cdk/index.js',
+    // Refer to the `public_api.js` files because the tests are not compiled with the
+    // Angular Compiler and therefore no `index.js` file will be generated.
+    '@angular/material': 'dist/packages/material/public_api.js',
+    '@angular/cdk': 'dist/packages/cdk/public_api.js',
   },
   packages: {
     // Thirdparty barrels.