.gitea/workflows/*: remove redundant config

All of the extra config is now being included by default with the github
action

.gitea/workflows/build-topology-graph.yml

@@ -13,13 +13,6 @@ jobs:
     - uses: actions/checkout@v6
 
     - uses: https://github.com/cachix/install-nix-action@v31
-      with:
-        extra_nix_config: |
-          show-trace = true
-          max-jobs = auto
-          trusted-users = root
-          experimental-features = nix-command flakes
-          build-users-group =
 
     - name: Build topology graph
       run: nix build .#topology -L