fix(ui5-checkbox): remove background from touchable area (#226)

Author: ilhan007

packages/main/src/themes/base/CheckBox.less

@@ -50,7 +50,6 @@ ui5-checkbox {
 	padding-left: .8125rem;
 	padding-right: 0.125rem;
 	box-sizing: border-box;
-	background: @sapUiFieldBackground;
 	outline: none;
 	position: relative;
 	-webkit-tap-highlight-color: rgba(0,0,0,0);
@@ -147,6 +146,7 @@ ui5-checkbox {
 	max-height: @_ui5_checkbox_inner_width_height;
 	border: @_ui5_checkbox_inner_border;
 	border-radius: @_ui5_checkbox_inner_border_radius;
+	background: @sapUiFieldBackground;
 	box-sizing: border-box;
 	position: relative;
 	cursor: default;