deps: update gax.version to v2.19.4

Author: renovate-bot

Diff for: first-party-dependencies/pom.xml

@@ -56,7 +56,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <site.installationModule>${project.artifactId}</site.installationModule>
     <grpc.version>1.50.1</grpc.version>
-    <gax.version>2.19.2</gax.version>
+    <gax.version>2.19.4</gax.version>
     <grpc-gcp.version>1.3.0</grpc-gcp.version>
     <gson.version>2.9.1</gson.version>
     <guava.version>31.1-jre</guava.version>