Bump GitHub Actions versions

These old versions will be deprecated soon. We couldn't update them
before because they required Node.js 20 which we now have from updating
to AlmaLinux 8.

Author: jwnrt

.github/workflows/toolchain_build.yml

@@ -48,8 +48,7 @@ jobs:
     timeout-minutes: 360
 
     steps:
-      # This uses checkout v3 instead of v4 because GitHub actions's nodejs 20 currently does not work on CentOS 7.
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup environment
         run: |
@@ -94,7 +93,7 @@ jobs:
             "${{ matrix.mcmodel }}" \
             "${{ matrix.cflags }}"
 
-      - uses: actions/upload-artifact@v3
+      - uses: actions/upload-artifact@v4
         with:
           name: ${{ matrix.name }}-toolchains
           path: ${{ env.ARTIFACT_STAGING_DIR }}