docs(docs-infra): modernize remaining shared-docs tests

Follow-up to 3a85031. Replace the last `fixture.detectChanges()` calls in
the shared-docs specs with `await fixture.whenStable()`, matching the
zoneless "act, wait, assert" pattern used by the rest of adev's tests.

Author: MeAkib

adev/shared-docs/components/slide-toggle/slide-toggle.component.spec.ts

@@ -31,14 +31,14 @@ describe('SlideToggle', () => {
     expect(component['checked']()).toBeTrue();
   });
 
-  it('should set active class for button when is checked', () => {
+  it('should set active class for button when is checked', async () => {
     component.checked.set(true);
-    fixture.detectChanges();
+    await fixture.whenStable();
     const buttonElement: HTMLButtonElement = fixture.nativeElement.querySelector('input');
     expect(buttonElement.classList.contains('docs-toggle-active')).toBeTrue();
 
     component.checked.set(false);
-    fixture.detectChanges();
+    await fixture.whenStable();
     expect(buttonElement.classList.contains('docs-toggle-active')).toBeFalse();
   });
 });

adev/shared-docs/components/viewers/docs-viewer/docs-viewer.component.spec.ts

@@ -238,12 +238,12 @@ describe('DocViewer', () => {
     expect(copyButton).toBeTruthy();
   });
 
-  it('should not leak any icon text content (so it stays out of the search index)', () => {
+  it('should not leak any icon text content (so it stays out of the search index)', async () => {
     const fixture = TestBed.createComponent(CopyLinkButton);
     fixture.componentRef.setInput('href', '#test-section');
     fixture.componentRef.setInput('label', 'Test Section');
     fixture.componentRef.setInput('matTooltip', 'Copy link to Test Section');
-    fixture.detectChanges();
+    await fixture.whenStable();
 
     expect(fixture.nativeElement.textContent.trim()).toBe('');
   });