style: enable rxjs/finnish (#6276)

chore(infra): use finnish notation for observables

do rename

packages/frontend/electron/src/helper/db/subjects.ts

@@ -1,7 +1,7 @@
 import { Subject } from 'rxjs';
 
 export const dbSubjects = {
-  externalUpdate: new Subject<{
+  externalUpdate$: new Subject<{
     workspaceId: string;
     update: Uint8Array;
     docId?: string;