Add missing self-hosted runner labels to central actionlint config

Add ubuntu-24.04-v64 which was previously only defined in per-repo
actionlint configs. This enables removing the redundant per-repo
actionlint config files.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: roryabraham

.github/actionlint.yml

@@ -9,6 +9,7 @@ self-hosted-runner:
     - macos-15-xlarge
     - macos-12
     - ubuntu-24.04-v4
+    - ubuntu-24.04-v64
     - blacksmith-2vcpu-ubuntu-2404
     - blacksmith-4vcpu-ubuntu-2404
     - blacksmith-8vcpu-ubuntu-2404