deps: update dependency io.grpc:grpc-bom to v1.40.0 (#438)

Author: renovate-bot

pom.xml

@@ -55,7 +55,7 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <site.installationModule>${project.artifactId}</site.installationModule>
 
-    <grpc.version>1.39.0</grpc.version>
+    <grpc.version>1.40.0</grpc.version>
     <gax.version>2.1.0</gax.version>
     <grpc-gcp.version>1.1.0</grpc-gcp.version>
     <guava.version>30.1.1-jre</guava.version>