[MJARSIGNER-67] Update Maven minimum to 3.6.3

Author: slachiewicz

pom.xml

@@ -69,7 +69,7 @@ under the License.
   </distributionManagement>
 
   <properties>
-    <mavenVersion>3.2.5</mavenVersion>
+    <mavenVersion>3.6.3</mavenVersion>
     <jacocoVersion>0.8.11</jacocoVersion>
     <project.build.outputTimestamp>2020-04-07T21:04:00Z</project.build.outputTimestamp>
   </properties>