(TODO remove) Temporarily run spec coverage against [1]

[1] ably/specification#282

Author: lawrence-forooghian

.github/workflows/check.yaml

@@ -53,7 +53,7 @@ jobs:
           xcode-version: 16.2
 
       - name: Spec coverage
-        run: swift run BuildTool spec-coverage
+        run: swift run BuildTool spec-coverage --spec-commit-sha 27ddbb3
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}