chore(core): deprecate $_kendo-data-uris usage

Author: epetrow

packages/core/scss/mixins/_data-uri.scss

@@ -1,6 +1,5 @@
 @import "./_border-radius.scss";
 @import "./_box-shadow.scss";
-@import "./_data-uri.scss";
 @import "./_disabled.scss";
 @import "./_decoration.scss";
 @import "./_focus-indicator.scss";