Stop running GitHub Actions in forked repos

.github/workflows/ci-notification.yml

@@ -4,6 +4,7 @@ on:
     types: [completed]
 jobs:
   notify:
+    if: github.repository == 'zeek/zeek'
     runs-on: ubuntu-latest
     steps:
       - name: Send CI Email Notification

.github/workflows/coverity-scan.yml

@@ -6,7 +6,9 @@ on:
 
 jobs:
   scan:
+    if: github.repository == 'zeek/zeek'
     runs-on: ubuntu-18.04
+
     steps:
       - uses: actions/checkout@v2