deps: gRPC upgrade to 1.43.2 (#567)

While we didn't wait for it, gRPC 1.43.2 became available now. The only change in gRPC 1.43.2 is the protobuf version upgrade.

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Fixes #<issue_number_goes_here> ☕️

Author: suztomo

first-party-dependencies/pom.xml

@@ -55,7 +55,7 @@
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <site.installationModule>${project.artifactId}</site.installationModule>
-    <grpc.version>1.43.1</grpc.version>
+    <grpc.version>1.43.2</grpc.version>
     <gax.version>2.8.1</gax.version>
     <grpc-gcp.version>1.1.0</grpc-gcp.version>
     <guava.version>31.0.1-jre</guava.version>