deps: update dependency io.grafeas:grafeas to v0.21.0 (#8)

Author: renovate-bot

pom.xml

@@ -170,7 +170,7 @@
       <dependency>
         <groupId>io.grafeas</groupId>
         <artifactId>grafeas</artifactId>
-        <version>0.20.0</version><!--{x-version-update:grafeas:current}-->
+        <version>0.21.0</version><!--{x-version-update:grafeas:current}-->
       </dependency>
       <!-- TODO: Until gax-grpc && grafeas align  -->
       <dependency>