fixed revision in pom

Author: FreeAndNil

pom.xml

@@ -25,7 +25,7 @@
   <packaging>pom</packaging>
   <groupId>org.apache.logging.log4net</groupId>
   <artifactId>apache-log4net</artifactId>
-  <version>3.1.0</version>
+  <version>${revision}</version>
   <name>Apache log4net</name>
   <description>Logging framework for Microsoft .NET Framework.</description>
   <url>https://logging.apache.org/log4net</url>