deps: update gax to v1.55.0 (#129)

Author: renovate-bot

pom.xml

@@ -67,7 +67,7 @@
     <google.api-common.version>1.8.1</google.api-common.version>
     <google.common-protos.version>1.17.0</google.common-protos.version>
     <google.iam.version>0.13.0</google.iam.version>
-    <gax.version>1.54.0</gax.version>
+    <gax.version>1.55.0</gax.version>
     <grpc.version>1.28.0</grpc.version>
     <protobuf.version>3.11.4</protobuf.version>
     <junit.version>4.13</junit.version>