fix(@schematics/angular): remove browser field from generated angular.json

The browser field is now optional with a default value of 'src/main.ts' as of commit c560d44.
This remove the explicit browser field from the application schematic template since it's no longer needed.

Author: cexbrayat

packages/schematics/angular/application/index.ts

@@ -295,7 +295,6 @@ function addAppToWorkspaceFile(options: ApplicationOptions, appDir: string): Rul
         builder: Builders.BuildApplication,
         defaultConfiguration: 'production',
         options: {
-          browser: `${sourceRoot}/main.ts`,
           polyfills: options.zoneless ? undefined : ['zone.js'],
           tsConfig: `${projectRoot}tsconfig.app.json`,
           inlineStyleLanguage,

packages/schematics/angular/application/index_spec.ts

@@ -387,7 +387,6 @@ describe('Application Schematic', () => {
       expect(prj.root).toEqual('');
       const buildOpt = prj.architect.build.options;
       expect(buildOpt.index).toBeUndefined();
-      expect(buildOpt.browser).toEqual('src/main.ts');
       expect(buildOpt.assets).toEqual([{ 'glob': '**/*', 'input': 'public' }]);
       expect(buildOpt.polyfills).toBeUndefined();
       expect(buildOpt.tsConfig).toEqual('tsconfig.app.json');
@@ -477,7 +476,6 @@ describe('Application Schematic', () => {
       const project = config.projects.foo;
       expect(project.root).toEqual('foo');
       const buildOpt = project.architect.build.options;
-      expect(buildOpt.browser).toEqual('foo/src/main.ts');
       expect(buildOpt.polyfills).toBeUndefined();
       expect(buildOpt.tsConfig).toEqual('foo/tsconfig.app.json');
       expect(buildOpt.assets).toEqual([{ 'glob': '**/*', 'input': 'foo/public' }]);