Remove java.level from pom (#625)

Author: lifeofguenter

pom.xml

@@ -29,7 +29,6 @@
     <changelist>999999-SNAPSHOT</changelist>
     <gitHubRepo>jenkinsci/bitbucket-branch-source-plugin</gitHubRepo>
     <jenkins.version>2.303.3</jenkins.version>
-    <java.level>8</java.level>
     <hpi.compatibleSinceVersion>2.0</hpi.compatibleSinceVersion>
   </properties>