Use github action that caches LFS files when checking out the repo (#647)

Uses https://github.com/nschloe/action-cached-lfs-checkout where we're using git-lfs.

This is a wrapper around `actions/checkout@v3` which uses `actions/cache@v3` to cache the files on LFS to avoid downloading them every time and spare LFS bandwidth.

.github/workflows/nightlyReports.yml

@@ -18,9 +18,7 @@ jobs:
     if: ${{ github.repository == 'vector-im/element-x-android' }}
     steps:
       - name: ⏬ Checkout with LFS
-        uses: actions/checkout@v3
-        with:
-          lfs: 'true'
+        uses: nschloe/action-cached-lfs-checkout@v1.2.1
 
       - name: Use JDK 17
         uses: actions/setup-java@v3