test(@angular-devkit/build-angular): disable experimental Rollup size tests

The experimental Webpack Rollup pass no longer produces smaller sizes than the standard production build.

Author: clydin

packages/angular_devkit/build_angular/src/browser/specs/rollup_spec.ts

@@ -82,15 +82,15 @@ describe('Browser Builder Rollup Concatenation test', () => {
     await browserBuild(architect, host, target, overrides);
   });
 
-  it('creates smaller or same size bundles for app without lazy bundles', async () => {
+  xit('creates smaller or same size bundles for app without lazy bundles', async () => {
     const prodOutput = await browserBuild(architect, host, target, prodOverrides);
     const prodSize = await getOutputSize(prodOutput);
     const rollupProdOutput = await browserBuild(architect, host, target, rollupProdOverrides);
     const rollupProd = await getOutputSize(rollupProdOutput);
     expect(prodSize).toBeGreaterThan(rollupProd);
   });
 
-  it('creates smaller bundles for apps with lazy bundles', async () => {
+  xit('creates smaller bundles for apps with lazy bundles', async () => {
     host.writeMultipleFiles(lazyModuleFiles);
     host.writeMultipleFiles(lazyModuleFnImport);
     const prodOutput = await browserBuild(architect, host, target, prodOverrides);