Temporarily disable nightly/main CI

Author: gwynne

.github/workflows/test.yml

@@ -22,7 +22,7 @@ jobs:
           - swift:5.8-jammy
           - swift:5.9-jammy
           - swiftlang/swift:nightly-5.10-jammy
-          - swiftlang/swift:nightly-main-jammy
+          #- swiftlang/swift:nightly-main-jammy
         include:
           - swift-image: swift:5.9-jammy
             code-coverage: true