ci: avoid unsupported Go 1.21 macOS pairing

Keep Go 1.21 coverage on Ubuntu and Windows while excluding current macOS runners, whose dyld rejects binaries emitted by the old internal linker because they lack LC_UUID.

Author: pyed

.github/workflows/ci.yml

@@ -21,6 +21,11 @@ jobs:
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
         go-version: [ '1.21.13', '1.26.7' ]
+        exclude:
+          # Go 1.21's internal linker omits LC_UUID, which current macOS
+          # runners require before they will execute test binaries.
+          - os: macos-latest
+            go-version: '1.21.13'
 
     steps:
     - name: Checkout repository