Set WOODPECKER_LIMIT_MEM to 6 GB for woodpecker

so pipelines don't get killed by OOM.

.woodpecker/flake-check.yaml

@@ -1,8 +0,0 @@
-when:
-  - event: pull_request
-
-steps:
-  - name: "Run nix flake check"
-    image: docker.nix-community.org/nixpkgs/nix-flakes
-    commands:
-      - nix flake check

config/hosts/woodpecker/woodpecker-server/woodpecker-server.nix

@@ -22,6 +22,7 @@
       WOODPECKER_DATABASE_DATASOURCE = "postgresql://woodpecker-server@/woodpecker-server?host=/run/postgresql";
       WOODPECKER_FORGEJO = "true";
       WOODPECKER_FORGEJO_URL = "https://git.hamburg.ccc.de";
+      WOODPECKER_LIMIT_MEM = "6442450944"; # 6GB
       # Set via enviornmentFile:
       # WOODPECKER_FORGEJO_CLIENT
       # WOODPECKER_FORGEJO_SECRET