Bump nexus-staging-maven-plugin from 1.6.3 to 1.6.8

Bumps nexus-staging-maven-plugin from 1.6.3 to 1.6.8.

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pom.xml

@@ -181,7 +181,7 @@
             <plugin>
                 <groupId>org.sonatype.plugins</groupId>
                 <artifactId>nexus-staging-maven-plugin</artifactId>
-                <version>1.6.3</version>
+                <version>1.6.8</version>
                 <extensions>true</extensions>
                 <configuration>
                     <serverId>ossrh</serverId>