also enable nightly swift in test runs

Author: ktoso

.github/workflows/pull_request.yml

@@ -45,7 +45,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        swift_version: ['6.1.2']
+        swift_version: ['6.1.2', 'nightly']
         os_version: ['jammy']
         jdk_vendor: ['corretto']
     container:
@@ -115,7 +115,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        swift_version: ['6.1.2']
+        swift_version: ['6.1.2', 'nightly']
         os_version: ['jammy']
         jdk_vendor: ['corretto']
     container:
@@ -185,7 +185,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        swift_version: ['6.1.2', 'nightly']
+        swift_version: ['6.1.2']  # no nightly testing on macOS
         os_version: ['macos']
         jdk_vendor: ['corretto']
         sample_app: [  # TODO: use a reusable-workflow to generate those names