removed some redundant code as a result of investigating 0004603

• assign to reporter was checking that user could handle
  the bug, not the new handler (already done in bug_api:bug_assign)
• added clarification to config for $g_update_bug_threshold

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@3026 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9