Upgrade eslint-plugin-matrix-org to 1.2.1

This upgrade came with a number of new lints that needed to be fixed across the code base. Primarily: explicit return types on functions, and explicit visibility modifiers on class members.

src/settings/submit-rageshake.ts

@@ -360,7 +360,7 @@ export function useRageshakeRequestModal(
   useEffect(() => {
     if (!client) return;
 
-    const onEvent = (event: MatrixEvent) => {
+    const onEvent = (event: MatrixEvent): void => {
       const type = event.getType();
 
       if (