Levitate: Only run against the main branch (#61401)

chore: only run Levitate against the main branch

.github/workflows/detect-breaking-changes-build-skip.yml

@@ -8,6 +8,8 @@ on:
   pull_request:
     paths-ignore:
       - "packages/**"
+    branches:
+      - 'main'
 
 jobs:
   detect:

.github/workflows/detect-breaking-changes-build.yml

@@ -7,6 +7,8 @@ on:
   pull_request:
     paths:
       - 'packages/**'
+    branches:
+      - 'main'
 
 jobs:
   buildPR: