Update dependency org.apache.maven.plugins:maven-gpg-plugin from v1.6 to v3

Author: renovate[bot]

gbfs-validator-java/pom.xml

@@ -63,7 +63,7 @@
         <maven-enforcer-plugin.version>3.5.0</maven-enforcer-plugin.version>
         <maven-source-plugin.version>3.3.1</maven-source-plugin.version>
         <maven-javadoc-plugin.version>3.11.2</maven-javadoc-plugin.version>
-        <maven-gpg-plugin.version>1.6</maven-gpg-plugin.version>
+        <maven-gpg-plugin.version>3.2.8</maven-gpg-plugin.version>
         <maven-compiler-plugin.version>3.14.0</maven-compiler-plugin.version>
         <maven-jar-plugin.version>3.4.2</maven-jar-plugin.version>
         <maven-clean-plugin.version>3.5.0</maven-clean-plugin.version>