Remove Swift 6.0.3 from test matrix

The codebase uses trailing commas in argument lists (BridgeJSToolInternal.swift)
which requires Swift 6.1+. Testing with 6.1.2 and 6.2 covers both SwiftSyntax
code paths (non-602 and 602).

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

Author: zhiqipan

.github/workflows/test.yml

@@ -64,7 +64,6 @@ jobs:
     strategy:
       matrix:
         swift-image:
-          - "swift:6.0.3"   # Tests with SwiftSyntax 600.x (non-SwiftSyntax602 code path)
           - "swift:6.1.2"   # Tests with SwiftSyntax 601.x (non-SwiftSyntax602 code path)
           - "swift:6.2"     # Tests with SwiftSyntax 602.x (SwiftSyntax602 code path)
     runs-on: ubuntu-latest