[maven-release-plugin] prepare for next development iteration

pom.xml

@@ -9,7 +9,7 @@
     <artifactId>release</artifactId>
     <packaging>hpi</packaging>
     <name>Jenkins Release Plugin</name>
-    <version>2.19</version>
+    <version>2.20-SNAPSHOT</version>
     <description>Adds the ability to wrap your job with pre- and post- build steps which are only executed when a manual
         release build is triggered.
     </description>
@@ -23,7 +23,7 @@
         <connection>scm:git:https://github.com/jenkinsci/release-plugin.git</connection>
         <developerConnection>scm:git:[email protected]:jenkinsci/release-plugin.git</developerConnection>
         <url>https://github.com/jenkinsci/release-plugin</url>
-        <tag>release-2.19</tag>
+        <tag>HEAD</tag>
     </scm>
 
     <dependencyManagement>