Use macOS 13 for Java 8 on GH CI

Author: garydgregory

.github/workflows/maven.yml

@@ -32,7 +32,7 @@ jobs:
         # Don't need 
         include:
           - java: 8
-            os: macos-latest
+            os: macos-13
             experimental: false
           - java: 8
             os: windows-latest