Revert 7910d8b for now.

Quite a few layouts seem to depend on the previous behavior, and there
isn't really an elegant way to resolve that for now, unless I miss
something in the lauout APIs. However, this does  need to be looked at
at some point, for some other controls as well, since it effectively
makes it impossible to properly use such controls in horizontal groups
and get an expected result.

src/kits/interface/CheckBox.cpp

@@ -452,7 +452,7 @@ BSize
 BCheckBox::MaxSize()
 {
 	return BLayoutUtils::ComposeSize(ExplicitMaxSize(),
-		_ValidatePreferredSize());
+		BSize(B_SIZE_UNLIMITED, _ValidatePreferredSize().height));
 }