Fix panning. (#3445)

We also need to clear the timeout when panning.


https://github.com/tldraw/tldraw/assets/2523721/f32fd4d0-332c-4a80-bed0-9ce49a68e1ab


https://github.com/tldraw/tldraw/assets/2523721/e97f5fac-083f-4f77-ab72-40701790f039

Had an [alternative
approach](https://github.com/tldraw/tldraw/pull/3444) of setting
timeouts and clearing them in dispatch, but since the timeout is 500ms I
think this should work as well.

### Change Type

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packages/editor/src/lib/editor/Editor.ts

@@ -8668,6 +8668,7 @@ export class Editor extends EventEmitter<TLEventMap> {
 						}
 
 						if (this.inputs.isPanning && this.inputs.isPointing) {
+							clearTimeout(this._longPressTimeout)
 							// Handle panning
 							const { currentScreenPoint, previousScreenPoint } = this.inputs
 							this.pan(Vec.Sub(currentScreenPoint, previousScreenPoint))