refactor(@angular/build): simplify update option passing in vitest executor

Author: maruthang

packages/angular/build/src/builders/unit-test/runners/vitest/executor.ts

@@ -356,7 +356,7 @@ export class VitestExecutor implements TestExecutor {
       cache: cacheOptions.enabled ? undefined : (false as const),
       testNamePattern: this.options.filter,
       watch,
-      ...(update ? { update } : {}),
+      update,
       ...(typeof ui === 'boolean' ? { ui } : {}),
       ...debugOptions,
     };