Merge pull request #2259 from kubernetes-client/dependabot/maven/com.google.protobuf-protobuf-java-3.21.0

Bump protobuf-java from 3.20.1 to 3.21.0

Author: k8s-ci-robot

pom.xml

@@ -45,7 +45,7 @@
     <snakeyaml.version>1.30</snakeyaml.version>
     <slf4j.version>1.7.36</slf4j.version>
     <caffeine.version>2.9.3</caffeine.version>
-    <protobuf.version>3.20.1</protobuf.version>
+    <protobuf.version>3.21.0</protobuf.version>
     <junit.version>4.13</junit.version>
     <bucket4j.version>7.5.0</bucket4j.version>
     <bouncycastle.version>1.70</bouncycastle.version>