fix timestamp format

Author: serenaponta

pom.xml

@@ -139,7 +139,7 @@
 		<maven.deploy.skip>true</maven.deploy.skip>
 
 		<!-- Used by several plugins, to make builds reproducible -->
-		<project.build.outputTimestamp>2021-12-13T15:09:42+0000</project.build.outputTimestamp>
+		<project.build.outputTimestamp>2021-12-13T15:09:42+00:00</project.build.outputTimestamp>
 	</properties>
 
 	<modules>