fix(registrar): allow for uppercase in top level domain of email

- There are many regexes for domain validation floating around
that require the top level domain to be lowercase, however I have
not found any reason for it to be so and most email validators
accept it uppercase aswell

perun-wui-core/src/main/java/cz/metacentrum/perun/wui/client/utils/Utils.java

@@ -1327,7 +1327,7 @@ public native static boolean isValidEmail(String email) /*-{
 		//var reg1 = /(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/; // not valid
 		//var reg2 = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/; // valid
 		//return !reg1.test(email) && reg2.test(email);
-		var reg4 = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-z]{2,}$/;
+		var reg4 = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
 		return reg4.test(email);
 	}-*/;