Drop using passphrase for maven-gpg-plugin

gpg-agent should be used

Author: slawekjaranowski

pom.xml

@@ -802,9 +802,6 @@ limitations under the License.
           <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-gpg-plugin</artifactId>
-            <configuration>
-              <passphrase>${gpg.passphrase}</passphrase>
-            </configuration>
             <executions>
               <execution>
                 <id>sign-artifacts</id>