fix lint: use let instead of const for $ref

Fixes lint no-const-assign.

packages/client/src/pages/admin/overview.user.vue

@@ -19,7 +19,7 @@ const props = defineProps<{
 	user: misskey.entities.User;
 }>();
 
-const chart = $ref(null);
+let chart = $ref(null);
 
 os.apiGet('charts/user/notes', { userId: props.user.id, limit: 16, span: 'day' }).then(res => {
 	chart = res;

packages/client/src/pages/gallery/post.vue

@@ -74,8 +74,8 @@ const props = defineProps<{
 	postId: string;
 }>();
 
-const post = $ref(null);
-const error = $ref(null);
+let post = $ref(null);
+let error = $ref(null);
 const otherPostsPagination = {
 	endpoint: 'users/gallery/posts' as const,
 	limit: 6,

packages/client/src/pages/theme-editor.vue

@@ -118,7 +118,7 @@ const fgColors = [
 	{ color: 'pink', forLight: '#84667d', forDark: '#e4d1e0', forPreview: '#b12390' },
 ];
 
-const theme = $ref<Partial<Theme>>({
+let theme = $ref<Partial<Theme>>({
 	base: 'light',
 	props: lightTheme.props,
 });