Drop 6.1.3 from CI

Author: marcprux

.github/workflows/pull_request.yml

@@ -147,7 +147,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        swift_version: ['6.1.3', '6.3', 'nightly']
+        swift_version: ['6.3', 'nightly']
         os_version: ['jammy']
         jdk_vendor: ['corretto']
     container: