pip-tools: add workflow_dispatch to be able to trigger it manually (#12642)

https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows#workflow_dispatch

Author: humitos

.github/workflows/pip-tools.yaml

@@ -10,6 +10,7 @@ on:
   schedule:
     # Run weekly on day 0 at 00:00 UTC
     - cron: "0 0 * * 0"
+  workflow_dispatch:
 
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