[Web] Fix onStart firing on Pan with activateAfterLongPress when gesture is disabled while being pressed down. (#3075)

## Description

`Pan` gesture allows for use of `activateAfterLongPress` modifier, which
allows it to be activated after holding down the gesture down for a
specified amount of time.

This modifier uses `setTimeout` underneath, which was not properly
cleared when the gesture was disabled while being pressed down.

Closes: #3074
## Test plan

- run the attached code
- when the button is clicked 2 times, nothing happens
- without this PR, clicking the button 2 times results in `onStart`
firing on the `Pan` gesture due to lack of `timeout` clearing

## Attached code
- make sure to have `@shopify/flash-list` installed
<details>
<summary>
Collapsed code
</summary>

```jsx
import React from 'react';
import { Button, View } from 'react-native';
import { FlashList } from '@shopify/flash-list';
import { Gesture, GestureDetector } from 'react-native-gesture-handler';

export default function HomeScreen() {
  const [enabled, setEnabled] = React.useState(true);
  const data = [0];

  const panGesture = Gesture.Pan()
    .enabled(enabled)
    .activateAfterLongPress(750)
    .onStart(() => {
      console.warn('pan triggered');
    });

  return (
    <GestureDetector gesture={panGesture}>
      <FlashList
        data={data}
        ListHeaderComponent={
          <Button
            title={enabled ? 'Disable Gestures' : 'Enable Gestures'}
            onPress={() => {
              setEnabled((prev) => !prev);
            }}
          />
        }
        renderItem={() => {
          return (
            <View
              style={{
                height: 70,
                backgroundColor: 'tomato',
              }}
            />
          );
        }}
      />
    </GestureDetector>
  );
}

```

</details>

## Results
<details>
<summary>
Collapsed results recordings
</summary>

### Before


https://github.com/user-attachments/assets/c09b2bc4-8b6a-4f2b-aa8c-efa78821d7f2

### Fixed


https://github.com/user-attachments/assets/5a72a363-94d4-4fdb-9060-f0f496487614

</details>

### Important:

As far as I see, all the other calls to `this.clearActivationTimeout()`
can be activated individually, and none of them are redundant.

Author: latekvo

src/web/handlers/PanGestureHandler.ts

@@ -268,6 +268,10 @@ export default class PanGestureHandler extends GestureHandler {
 
     this.tracker.removeFromTracker(event.pointerId);
 
+    if (this.tracker.getTrackedPointersCount() === 0) {
+      this.clearActivationTimeout();
+    }
+
     if (this.currentState === State.ACTIVE) {
       this.end();
     } else {