Delete ehcache-core-2.6.9 tag to retag.

git-svn-id: http://svn.terracotta.org/svn/ehcache@8932 b9324663-ca0f-0410-8574-be9b3887307d
Tag ehcache-core-2.6.9 from 3.7.8-rc branch

git-svn-id: http://svn.terracotta.org/svn/ehcache@8933 b9324663-ca0f-0410-8574-be9b3887307d