Allow triggering validate-apis CI (#5595) (#5608)

It can be useful to update the cache.

(cherry picked from commit 0460584)

Co-authored-by: Quentin Pradet <[email protected]>

Author: github-actions[bot]

.github/workflows/validate-apis.yml

@@ -1,6 +1,7 @@
 name: Validate APIs
 
 on:
+  workflow_dispatch:
   pull_request:
     branches:
       - main