gui/language_selection: Don't force even height for language column

While it sounds like a great idea on paper, in practice having the
language column have the same height on all rows causes issues because
of at least one entry having an unusually tall label because of
non-Latin characters involved in it.

[label] does not support setting the vertical alignment of text — only
the vertical alignment of the widget itself can be set. This doesn't
help in this case because the widget is always as tall as its row —
it's the text's positioning that needs adjusting.

It turns out to be a better look to have all text be vertically
centered by not letting the label's height be dictated by the row's,
and let the layout engine center the label if needed for any reason.

data/gui/window/language_selection.cfg

@@ -164,7 +164,7 @@ If you are a first-time player, we recommend using a mostly-complete translation
 		[linked_group]
 			id = "language"
 			fixed_width = true
-			fixed_height = true
+			fixed_height = false
 		[/linked_group]
 
 		[linked_group]