[native] fix handling logout action

Summary:
Fix for a regression introduced in D9010.

The problem was that the previous code returned immediately which means `baseReducer` wasn't able to properly modify the state.

Not a huge fan of this solution but I saw this somewhere in the codebase. As an alternative, I can suggest:
1. Creating a separate reducer and running it in the same place - don't think is much better, will require the same assignment.
2. Creating separate reduce and moving this to lib.

Only 2 seem better than this, but don't want to put native-specific data in lib.

Test Plan: Using Redux DevTools make sure that logout is handled and data that needs to be cleared is cleared/set default where it needs to be.

Reviewers: ginsu, michal, tomek

Reviewed By: tomek

Subscribers: ashoat, wyilio

Differential Revision: https://phab.comm.dev/D9674

native/redux/redux-setup.js

@@ -182,9 +182,11 @@ function reducer(state: AppState = defaultState, action: Action) {
     action.type === logOutActionTypes.success ||
     action.type === deleteAccountActionTypes.success
   ) {
-    return {
+    state = {
       ...state,
-      localSettings: { isBackupEnabled: false },
+      localSettings: {
+        isBackupEnabled: false,
+      },
     };
   }
 
@@ -290,6 +292,7 @@ type FixUnreadActiveThreadResult = {
   +state: AppState,
   +threadStoreOperations: $ReadOnlyArray<ThreadStoreOperation>,
 };
+
 function fixUnreadActiveThread(
   state: AppState,
   action: *,
@@ -336,6 +339,7 @@ function fixUnreadActiveThread(
 }
 
 let appLastBecameInactive = 0;
+
 function appBecameInactive() {
   appLastBecameInactive = Date.now();
 }