ci: minor optimization in the cancel workflow (#10978)

before this we scheduled two additional workflows, one for each workflow.
This PR now schedules just one, which cancels both workflows by itself.

.github/workflows/cancel.yml

@@ -2,7 +2,7 @@ name: Cancel previous workflows
 
 on:
   workflow_run:
-    workflows: ["Code CI", "Sanitized CI"] # the other workflows finish quickly - no need to skip them for now
+    workflows: ["Code CI"]
     types:
       - requested
 
@@ -14,4 +14,5 @@ jobs:
       # don't cancel CI for commits pushed to vlang/v#master (if ci is still too slow, this can be removed safely)
       if: ${{ github.event.workflow_run.head_repository.full_name != 'vlang/v' || github.event.workflow_run.head_branch != 'master' }}
       with:
-        workflow_id: ${{ github.event.workflow.id }}
+        # workflow ids for `Code CI` and `Sanitized CI` (from https://api.github.com/repos/vlang/v/actions/workflows):
+        workflow_id: 4577,7940868 # the other workflows finish quickly - no need to skip them