call focus() should focus only when _autoFocus is true for autoFocus directive

Currently focus() works regardless of autoFocus state.

PiperOrigin-RevId: 199233319

Author: Googler

lib/focus/focus.dart

@@ -175,6 +175,8 @@ class AutoFocusDirective extends RootFocusable implements OnInit, OnDestroy {
 
   @override
   void focus() {
+    if (!_autoFocus) return;
+
     if (_focusable != null) {
       _focusable.focus();
     } else {