gui2/preferences: Streamline filter options on the Hotkeys page

Categories vs. Filter both deal with filtering -- the only difference is
that categories has a broader scope than the name-based filtering, with
the latter being applied to results for the selected categories. We
don't need two rows for both.

data/gui/window/preferences/02_hotkeys.cfg

@@ -22,7 +22,7 @@
 
 						[label]
 							definition = "default"
-							label = _ "Categories:"
+							label = _ "Filter:"
 						[/label]
 					[/column]
 
@@ -39,26 +39,9 @@
 						[/multimenu_button]
 					[/column]
 
-				[/row]
-
-				[row]
-
-					[column]
-						grow_factor = 0
-						border = "all"
-						border_size = 5
-
-						[label]
-							definition = "default"
-							label = _ "Filter:"
-						[/label]
-					[/column]
-
 					[column]
-						grow_factor = 1
 						border = "all"
 						border_size = 5
-						horizontal_grow = true
 
 						[text_box]
 							id = "filter"