Update update-swift-version.yml (#131)

Avoid running update swift version workflow on every PR.

Author: rauhul

.github/workflows/update-swift-version.yml

@@ -1,8 +1,6 @@
 name: Update Swift Version
 
 on:
-  pull_request:
-    types: [opened, reopened, synchronize]
   schedule:
     - cron: '0 0 */14 * *'  # Every 14 days at midnight UTC
   workflow_dispatch: