Switching the unassignment automation to use the central script from Hacktoberfest repo (#2037)

* Swapping to call shared workflow

* Rename pr-auto-unassign-stale.yml to unassign-stale.yml

* Delete .github/workflow/unassign-stale.yml

* Create unassign-stale.yml

Switching the automation to shim that calls the central one

Author: Lacah

.github/workflows/pr-auto-unassign-stale.yml

@@ -0,0 +1,23 @@
+name: Unassign stale PR assignees
+on:
+  schedule:
+    - cron: "*/15 * * * *"
+  workflow_dispatch:
+    inputs:
+      enabled:         { type: boolean, default: true }
+      max_age_minutes: { type: number,  default: 60 }
+      dry_run:         { type: boolean, default: false }
+
+permissions:
+  pull-requests: write
+  issues: write
+  contents: read
+
+jobs:
+  call:
+    uses: ServiceNowDevProgram/Hacktoberfest/.github/workflows/unassign-stale.yml@main
+    with:
+      enabled:         ${{ inputs.enabled }}
+      max_age_minutes: ${{ inputs.max_age_minutes }}
+      dry_run:         ${{ inputs.dry_run }}
+    secrets: inherit