nix-cache: remove unused Gitea Actions runner

The actions runner on nix-cache01 was never actively used.
Removing it before migrating to nix-cache02.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

terraform/vault/secrets.tf

@@ -81,12 +81,6 @@ locals {
       data          = { key = var.cache_signing_key }
     }
 
-    # Gitea Actions runner token
-    "hosts/nix-cache01/actions-token" = {
-      auto_generate = false
-      data          = { token = var.actions_token_1 }
-    }
-
     # Homelab-deploy NKeys
     "shared/homelab-deploy/listener-nkey" = {
       auto_generate = false