Removed Ambiguity :workflow_dispatch statement about "default branch" (…

…#35727)

Co-authored-by: Alex Nguyen <150945400+nguyenalex836@users.noreply.github.com>

data/reusables/actions/branch-requirement.md

@@ -1,2 +1,2 @@
 > [!NOTE]
-> This event will only trigger a workflow run if the workflow file is on the default branch.
+> This event will only trigger a workflow run if the workflow file exists on the default branch.