Fix spell 6346 (Fear Ward)

Add missing proc mask for spell 6346 (Fear Ward)

This commit [84e3d1c](http://github.com/mangos-zero/server-old/commit/84e3d1c) is one of those pending backports from old mangos-zero concatenated in: https://github.com/cmangos/issues/wiki/classic_backporting-todo-zero-commits

I tested it and this is my report:
> This spell is already flagged as intented in classic db (inherited from old mangos-zero database). This commit should be applied nonetheless to keep track of the fix.