chore: Pin REST API version for Renovate dispatch (#2594)

Pin `X-GitHub-Api-Version` to `2026-03-10` on the Renovate workflow
dispatch so the step stops warning that the default `2022-11-28` API
version is scheduled for removal.

Author: erezrokah

.github/workflows/release-pr.yml

@@ -59,4 +59,7 @@ jobs:
               repo: '.github',
               workflow_id: 'renovate.yml',
               ref: 'main',
+              headers: {
+                'X-GitHub-Api-Version': '2026-03-10',
+              },
             })