Merge branch 'slashmanov/migrate-diffs-getters-spec-to-pinia' into 'master'

Migrate legacy diffs Vuex getters spec to Pinia

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/167176



Merged-by: Phil Hughes <me@iamphill.com>
Approved-by: Phil Hughes <me@iamphill.com>
Co-authored-by: Stanislav Lashmanov <slashmanov@gitlab.com>

app/assets/javascripts/mr_notes/store/legacy_mr_notes.js

 import { defineStore } from 'pinia';
 
-export const useMrNotes = defineStore('legacyMrNotes', {});
+export const useMrNotes = defineStore('legacyMrNotes', {
+  state() {
+    return {
+      page: {
+        mrMetadata: {},
+      },
+    };
+  },
+});