fix(iOS): apply accessibility props to the indicator in ActivityIndicator

The accessibility props of ActivityIndicator went to the host view, which
is not an accessibility element, so VoiceOver read the inner
UIActivityIndicatorView with its default label. Return the indicator from
accessibilityElement, as RCTSwitchComponentView does for UISwitch.

Author: faciledictu

packages/react-native/React/Fabric/Mounting/ComponentViews/ActivityIndicator/RCTActivityIndicatorViewComponentView.mm

@@ -91,6 +91,18 @@ - (void)updateProps:(const Props::Shared &)props oldProps:(const Props::Shared &
   [super updateProps:props oldProps:oldProps];
 }
 
+// UIActivityIndicatorView is the accessibility element, not this view, so the
+// accessibility props go to it.
+- (BOOL)isAccessibilityElement
+{
+  return NO;
+}
+
+- (NSObject *)accessibilityElement
+{
+  return _activityIndicatorView;
+}
+
 @end
 
 Class<RCTComponentViewProtocol> RCTActivityIndicatorViewCls(void)