Removed submit button disabling javascript.
With the fix for 0009323, Firefox 3 maintains button state as disabled when you back, preventing users from trying again.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@5459 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9