Removed text-shadow from input-group-addon (#2341)

Removed text-shadow from input-group-addon to match bootstrap3 input-group-addon

Author: joaobhering

less/datepicker3.less

@@ -250,7 +250,6 @@
 		min-width: 16px;
 		padding: 4px 5px;
 		line-height: @line-height-base;
-		text-shadow: 0 1px 0 #fff;
 		border-width: 1px 0;
 		margin-left: -5px;
 		margin-right: -5px;