Theme: Removes css for ui-state-checked its not used any more

Also updates checkbox icon border color to go with background color
Ref jquery/download.jqueryui.com#335
Fixes #15059
Closes gh-1753

Author: arschmitz

themes/base/theme.css

@@ -116,9 +116,8 @@ a.ui-button:active,
 	font-weight: normal/*{fwDefault}*/;
 	color: #ffffff/*{fcActive}*/;
 }
-.ui-icon-background,
-.ui-state-active .ui-icon-background {
-	border: #003eff/*{borderColorActive}*/;
+.ui-icon-background {
+	border: #dddddd/*{borderColorContent}*/;
 	background-color: #ffffff/*{bgColorContent}*/;
 }
 .ui-state-active a,
@@ -137,10 +136,6 @@ a.ui-button:active,
 	background: #fffa90/*{bgColorHighlight}*/ /*{bgImgUrlHighlight}*/ /*{bgHighlightXPos}*/ /*{bgHighlightYPos}*/ /*{bgHighlightRepeat}*/;
 	color: #777620/*{fcHighlight}*/;
 }
-.ui-state-checked {
-	border: 1px solid #dad55e/*{borderColorHighlight}*/;
-	background: #fffa90/*{bgColorHighlight}*/;
-}
 .ui-state-highlight a,
 .ui-widget-content .ui-state-highlight a,
 .ui-widget-header .ui-state-highlight a {