ci: use github-actions bot account for commits

Author: CompeyDev

.github/workflows/nix-flake-update.yml

@@ -36,6 +36,8 @@ jobs:
 
       - uses: DeterminateSystems/update-flake-lock@v27
         with:
+          git-committer-name: "github-actions[bot]"
+          git-committer-email: "41898282+github-actions[bot]@users.noreply.github.com"
           pr-title: "Update Nix flake inputs" 
           pr-labels: |
             automated