Update build.yml

Update to released version of 5.6.

Author: compnerd

.github/workflows/build.yml

@@ -23,8 +23,8 @@ jobs:
           - branch: swift-5.5.3-release
             tag: 5.5.3-RELEASE
 
-          - branch: swift-5.6-branch
-            tag: 5.6-DEVELOPMENT-SNAPSHOT-2022-02-07-a
+          - branch: swift-5.6-release
+            tag: 5.6-RELEASE
 
           - branch: development
             tag: DEVELOPMENT-SNAPSHOT-2022-03-09-a