Drop Swift 6.1 from Windows and exclude wasm for Swift <=6.1 on Ubuntu

swift-docc-plugin 1.4.6 is incompatible with Swift 6.1 on Windows (missing
Lock, SnippetExtractor, ParsedSymbolGraphArguments types). Windows matrix
now covers 6.2 and 6.3 only.

WASM/wasm-embedded tooling does not support Swift 6.0 or 6.1 on Ubuntu,
so those combinations are excluded from the build matrix.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: leogdion

.github/workflows/SyntaxKit.yml

@@ -109,8 +109,6 @@ jobs:
             build: 6.3-RELEASE
           - version: swift-6.2-release
             build: 6.2-RELEASE
-          - version: swift-6.1-release
-            build: 6.1-RELEASE
     steps:
       - uses: actions/checkout@v6
       - uses: brightdigit/swift-build@v1.5.2