fix(ui): increase z index for Slideover and Modal (#2758)

In #2725 there were changes to z-index of header and Slideover and Modal
is behind the header. It's visible in creating new token/namespace or in
any modal dialog

ui/src/components/Modal.tsx

@@ -12,7 +12,7 @@ export default function Modal(props: ModalProps) {
 
  return (
  <Transition.Root show={open} as={Fragment}>
- <Dialog as="div" className="relative z-10" onClose={setOpen}>
+ <Dialog as="div" className="relative z-20" onClose={setOpen}>
  <Transition.Child
  as={Fragment}
  enter="ease-out duration-200"

ui/src/components/Slideover.tsx

@@ -14,7 +14,7 @@ const SlideOver = forwardRef((props: SlideOverProps, ref: any) => {
  <Transition.Root show={open} as={Fragment}>
  <Dialog
  as="div"
- className="relative z-10"
+ className="relative z-20"
  onClose={setOpen}
  initialFocus={ref}
  >