Update build.yml

Update 5.7 train to 5.7.3.

Author: compnerd

.github/workflows/build.yml

@@ -29,8 +29,8 @@ jobs:
             tag: 5.6.1-RELEASE
             options: ''
 
-          - branch: swift-5.7-release
-            tag: 5.7-RELEASE
+          - branch: swift-5.7.3-release
+            tag: 5.7.3-RELEASE
             options: ''
 
           - branch: development