Deletes the org.teiid.8.2.x submodule

* To fully remove all references to this submodule, local repositories
  should do the following:
 * Remove the submodule reference in the main repository's .git/config file
 * Remove the actual directory 'plugins/teiid/org.teiid.8.2.x'

* This should result in the repository being clean and 8.2.x free