comment out the pugin of "maven-gpg-plugin"

[chengyunyong]

                        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-gpg-plugin</artifactId>
            <version>1.6</version>
            <executions>
                <execution>
                    <id>sign-artifacts</id>
                    <phase>verify</phase>
                    <goals>
                        <goal>sign</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>