update ossrh plugin to fix API mismatch error

Author: abyrd

pom.xml

@@ -83,7 +83,7 @@
                 <!-- Recommended way to deploy to OSSRH -->
                 <groupId>org.sonatype.plugins</groupId>
                 <artifactId>nexus-staging-maven-plugin</artifactId>
-                <version>1.6.7</version>
+                <version>1.6.12</version>
                 <extensions>true</extensions>
                 <configuration>
                     <serverId>ossrh</serverId>