refactor(@angular/build): remove deprecated browser-level isolate option

This commit removes the deprecated `isolate` option from the browser-level configuration for the Vitest runner.

The `browser.isolate` option has been deprecated in Vitest. Test isolation should now be controlled at the test level, which is already the default behavior. This change aligns the builder with the latest Vitest practices and removes a deprecated setting.

(cherry picked from commit 6f2d4a9)

Author: clydin

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

@@ -117,7 +117,6 @@ export async function setupBrowserConfiguration(
     provider,
     headless,
     ui: !headless,
-    isolate: debug,
     viewport,
     instances: browsers.map((browserName) => ({
       browser: normalizeBrowserName(browserName),