fix: re-enable spectesting.yml (#15659)

Author: ncooke3

.github/workflows/spectesting.yml

@@ -4,7 +4,7 @@ on:
   workflow_dispatch:
   pull_request:
     branches:
-      - none
+      - main
 
 concurrency:
     group: ${{ github.workflow }}-${{ github.head_ref || github.ref }}