chore(deps): update actions/cache action to v5 (#815)

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Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/buildtest.yaml

@@ -28,7 +28,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           path: |
             ~/go/pkg/mod