ci: Remove Swift nightly 6.2 from Ubuntu build matrix

Remove redundant Swift nightly 6.2 build since we already test against
the stable Swift 6.2 release.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: leogdion

.github/workflows/BushelKit.yml

@@ -15,7 +15,6 @@ jobs:
         image:
           - swift:6.1
           - swift:6.2
-          - swiftlang/swift:nightly-6.2-noble
           - swiftlang/swift:nightly-6.3-noble
     container: ${{ matrix.image }}
     steps: