Add v1.13.0 release of grpc-java

tools/interop_matrix/client_matrix.py

@@ -172,6 +172,9 @@ LANG_RELEASE_MATRIX = {
         {
             'v1.12.0': None
         },
+        {
+            'v1.13.0': None
+        },
     ],
     'python': [
         {