[Global Search] Return focus to live region after page re-render even when left nav is open (#186430)

## Summary

Closes https://github.com/elastic/kibana/issues/186423 

This code is interfering with the focus to the ScreenReaderLive region
which is needed to announce page renders for assistive technologies.

### After


https://github.com/user-attachments/assets/8b6141d1-201c-47fd-9c03-992ae7f275ce

Note the active element after the click is now the EuiScreenReaderOnly
element to announce the page title

### To Test

Add `document.activeElement` in the developer tools console to see what
element is active when testing keyboard navigation. After clicking a
link, it should return focus to the ScreenReaderLive component to
announce the page title to the user.

packages/core/chrome/core-chrome-browser-internal/src/ui/header/header.tsx

@@ -182,9 +182,6 @@ export function Header({
                   onIsLockedUpdate={onIsLockedUpdate}
                   closeNav={() => {
                     setIsNavOpen(false);
-                    if (toggleCollapsibleNavRef.current) {
-                      toggleCollapsibleNavRef.current.focus();
-                    }
                   }}
                   customNavLink$={observables.customNavLink$}
                   button={