Use paginated tree for the last commit query

What does this MR do and why?

We don't need a tree at all for the last commit, but since the existing paginated tree returns a limited number of entries, we can use it without introducing backend changes

app/assets/javascripts/repository/components/last_commit.vue

@@ -49,10 +49,11 @@ export default {
         };
       },
       update: (data) => {
-        const pipelines = data.project?.repository?.tree?.lastCommit?.pipelines?.edges;
+        const lastCommit = data.project?.repository?.paginatedTree?.nodes[0]?.lastCommit;
+        const pipelines = lastCommit?.pipelines?.edges;
 
         return {
-          ...data.project?.repository?.tree?.lastCommit,
+          ...lastCommit,
           pipeline: pipelines?.length && pipelines[0].node,
         };
       },