ci: avoid repeat running for PR from self

Author: waketzheng

.github/workflows/ci.yml

@@ -2,12 +2,13 @@ name: ci
 on:
   push:
     branches-ignore:
-      - master
+      - main
   pull_request:
     branches-ignore:
       - master
 jobs:
   test:
+    if: ${{ !(github.event_name == 'pull_request' && github.event.pull_request.base.repo.full_name == github.repository) }}
     runs-on: ubuntu-22.04
     services:
       mssql:
@@ -57,6 +58,7 @@ jobs:
           COVERALLS_PARALLEL: true
 
   coveralls:
+    if: ${{ !(github.event_name == 'pull_request' && github.event.pull_request.base.repo.full_name == github.repository) }}
     name: Finish Coveralls
     needs: test
     runs-on: ubuntu-22.04