[STYLE] Select2 input box - add border-radius
[STYLE] Select2 input box - add border-radius

The border-radius is not added to the input box, but to its ancestor
<ul> with class `select2-choices`.

Signed-off-by: Pang Yan Han <22594c345857f664c61cd411f607c4d40a9d4af9@gmail.com>

yanhan/cljs-nusmods,yanhan/cljs-nusmods,yanhan/cljs-nusmods