fix: downgrading nexus staging plugin 1.6.8 (googleapis#871)

Author: suztomo

pom.xml

@@ -142,7 +142,7 @@
         <plugin>
           <groupId>org.sonatype.plugins</groupId>
           <artifactId>nexus-staging-maven-plugin</artifactId>
-          <version>1.6.11</version>
+          <version>1.6.8</version>
           <extensions>true</extensions>
           <configuration>
             <serverId>ossrh</serverId>