[build] Updaate github checkout action.

Seems like `checkout@v2` is being deprecated. Update to v3.

.github/workflows/musl-build-image.yml

@@ -20,7 +20,7 @@ jobs:
     steps:
       -
         name: checkout code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       -
         name: Set up QEMU
         uses: docker/setup-qemu-action@v2

.github/workflows/rpmbuild.yml

@@ -15,7 +15,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Get the release version from the tag
         shell: bash