Remove out of date RELEASE-PLAN document

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/codec/trunk@801129 13f79535-47bb-0310-9956-ffa450edef68

Author: Niall Kegan Pemberton

RELEASE-PLAN

@@ -33,7 +33,6 @@
                 <include>NOTICE.txt</include>
                 <include>pom.xml</include>
                 <include>RELEASE-NOTES*.txt</include>
-                <include>RELEASE-PLAN</include>
                 <include>TODO</include>
             </includes>
         </fileSet>