revert to old maven gpg version

Author: martinspielmann

pom.xml

@@ -14,7 +14,7 @@
     <sonar-maven-plugin.version>3.7.0.1746</sonar-maven-plugin.version>
     <nexus-staging-maven-plugin.version>1.6.13</nexus-staging-maven-plugin.version>
     <maven-source-plugin.version>3.2.0</maven-source-plugin.version>
-    <maven-gpg-plugin.version>3.0.1</maven-gpg-plugin.version>
+    <maven-gpg-plugin.version>1.6</maven-gpg-plugin.version>
 	</properties>
 	<url>https://github.com/martinspielmann/java-nmap-xml-parser</url>
 
@@ -136,4 +136,4 @@
       </distributionManagement>
     </profile>
   </profiles>
-</project>
+</project>