CI: Update actions (#684)

Silent deprecation warning

Author: rhaschke

.github/workflows/ci_bionic.yml

@@ -25,10 +25,10 @@ jobs:
 
     steps:
       - name: Fetch repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: ccache cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ${{ env.CCACHE_DIR }}
           # we always want the ccache cache to be persisted, as we cannot easily

.github/workflows/ci_focal.yml

@@ -25,10 +25,10 @@ jobs:
 
     steps:
       - name: Fetch repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: ccache cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ${{ env.CCACHE_DIR }}
           # we always want the ccache cache to be persisted, as we cannot easily