test: update css minification spec to match new Esbuild output

For more context see https://github.com/evanw/esbuild/blob/master/CHANGELOG.md#%E2%80%8B0137

(cherry picked from commit ba54a8d)

Author: alan-agius4

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

@@ -729,7 +729,7 @@ describe('Browser Builder styles', () => {
       host.replaceInFile('tsconfig.json', 'es2017', 'es5');
 
       result = await browserBuild(architect, host, target, { optimization: true, aot: true });
-      expect(await result.files['main.js']).toContain('rgba(0,0,0,.149)');
+      expect(await result.files['main.js']).toContain('rgba(0,0,0,.15)');
     });
   });
 });