deps: update gax.version to v1.50.1 (#38)

Author: renovate-bot

pom.xml

@@ -154,7 +154,7 @@
     <google.core.version>1.90.0</google.core.version>
     <google.api-common.version>1.8.1</google.api-common.version>
     <google.common-protos.version>1.17.0</google.common-protos.version>
-    <gax.version>1.49.1</gax.version>
+    <gax.version>1.50.1</gax.version>
     <grpc.version>1.25.0</grpc.version>
     <protobuf.version>3.10.0</protobuf.version>
     <junit.version>4.12</junit.version>