deps: update gax.version to v2.4.0 (#458)

* deps: update dependency com.google.api:gax-bom to v2.4.0

* chore: update to 2.4.0

Co-authored-by: Emily Ball <emilyball@google.com>

first-party-dependencies/pom.xml

@@ -55,9 +55,8 @@
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <site.installationModule>${project.artifactId}</site.installationModule>
-
     <grpc.version>1.40.1</grpc.version>
-    <gax.version>2.3.0</gax.version>
+    <gax.version>2.4.0</gax.version>
     <grpc-gcp.version>1.1.0</grpc-gcp.version>
     <guava.version>30.1.1-jre</guava.version>
     <protobuf.version>3.17.3</protobuf.version>
@@ -189,4 +188,4 @@
       </dependency>
     </dependencies>
   </dependencyManagement>
-</project>
+</project>