Update gax.version to 1.47.1. (#5656)

Author: kolea2

google-cloud-clients/pom.xml

@@ -156,7 +156,7 @@
     <bom.version>0.98.1-alpha-SNAPSHOT</bom.version><!-- {x-version-update:google-cloud-bom:current} -->
     <api-client.version>1.30.2</api-client.version>
     <!-- make sure to keep gax version in sync with google-cloud-bom -->
-    <gax.version>1.46.1</gax.version>
+    <gax.version>1.47.1</gax.version>
     <api.common.java.version>1.8.1</api.common.java.version>
     <google.auth.version>0.16.2</google.auth.version>
     <grpc.version>1.21.0</grpc.version>