remove 'height: 550px;' from taxonomy_manager.css

I think we should remove the 'height' attribute from line 34 of taxonomy_manager.css so that the default height of the widow is the number of items returned as specified in the taxonomy manager settings. I end up over-riding this every time.

so the new css would be:

#taxonomy2-manager-tree-outer-div,
#taxonomy-manager-tree-outer-div {	
  overflow: auto;
  width: 46%;
}