cancel the debounce in the cleanup function that actually handles the event setup and teardown, where it belongs

Signed-off-by: Morgan Bentell <mbentell@spotify.com>

plugins/techdocs-react/src/hooks.ts

@@ -82,18 +82,15 @@ export const useShadowRootSelection = (waitMillis: number = 0) => {
     [shadowRoot, setSelection, waitMillis],
   );
 
-  useEffect(() => {
-    // cancel debounce on unmount
-    return () => handleSelectionChange.cancel();
-  }, [handleSelectionChange]);
-
   useEffect(() => {
     window.document.addEventListener('selectionchange', handleSelectionChange);
-    return () =>
+    return () => {
+      handleSelectionChange.cancel();
       window.document.removeEventListener(
         'selectionchange',
         handleSelectionChange,
       );
+    };
   }, [handleSelectionChange]);
 
   return selection;