test: disable buildOptimizer for server tests

Attempting to reduce flaky tests.

Author: alan-agius4

packages/angular_devkit/build_angular/src/builders/server/tests/setup.ts

@@ -28,4 +28,5 @@ export const BASE_OPTIONS = Object.freeze<Schema>({
 
   // Disable optimizations
   optimization: false,
+  buildOptimizer: false,
 });