[iOS] Fix buttons crash when unmounting children (#4065)

## Description

`buttonView` is `UIControl`, which unlike `RCTViewComponentView` does
strict checks for view index when unmounting children.

Fixes #4062

## Test plan

<details>
<summary>Tested on example from #4062</summary>

```tsx
import { useState } from 'react';
import { Pressable, Text, View } from 'react-native';
import {
  Clickable,
  GestureHandlerRootView,
} from 'react-native-gesture-handler';

export default function App() {
  const [children, setChildren] = useState<React.ReactNode[]>([]);

  return (
    <GestureHandlerRootView
      style={[
        { flex: 1, alignItems: 'center', justifyContent: 'center' },
        { marginTop: 25 },
      ]}>
      <Clickable>
        <Text>Clickable</Text>

        {children.map((child, index) => (
          <View key={index}>{child}</View>
        ))}
      </Clickable>

      <Pressable
        onPress={() =>
          setChildren([
            ...children,
            <Text key={children.length}>New child</Text>,
          ])
        }>
        <Text>Add child to Clickable</Text>
      </Pressable>

      <Pressable onPress={() => setChildren(children.slice(0, -1))}>
        <Text>Remove child from Clickable</Text>
      </Pressable>
    </GestureHandlerRootView>
  );
}
```

</details>

Author: m-bert

packages/react-native-gesture-handler/apple/RNGestureHandlerButtonComponentView.mm

@@ -72,9 +72,12 @@ - (void)mountChildComponentView:(RNGHUIView<RCTComponentViewProtocol> *)childCom
   [_buttonView mountChildComponentView:childComponentView index:index];
 }
 
-- (void)unmountChildComponentView:(RNGHUIView<RCTComponentViewProtocol> *)childComponentView index:(NSInteger)index
+- (void)unmountChildComponentView:(RNGHUIView<RCTComponentViewProtocol> *)childComponentView
+                            index:(NSInteger)__unused index
 {
-  [_buttonView unmountChildComponentView:childComponentView index:index];
+  if (childComponentView.superview == _buttonView) {
+    [childComponentView removeFromSuperview];
+  }
 }
 
 - (LayoutMetrics)buildWrapperMetrics:(const LayoutMetrics &)metrics