Add grpc-java v1.30.2 to interop test client matrix

Author: sanjaypujare

tools/interop_matrix/client_matrix.py

@@ -221,6 +221,7 @@ def __init__(self, patch=[], runtimes=[], testcases_file=None):
             ('v1.29.0', ReleaseInfo()),
             ('v1.30.0', ReleaseInfo()),
             ('v1.30.1', ReleaseInfo()),
+            ('v1.30.2', ReleaseInfo()),
         ]),
     'python':
         OrderedDict([