style: use style props

Author: iuex

src/components/Quiz/QuizzesModal.tsx

@@ -40,7 +40,7 @@ const QuizzesModal = ({
       <ModalOverlay bg="blackAlpha.700" />
 
       <Center as={ModalContent} m={0} bg={getStatusColor()} py="16">
-        <ModalCloseButton size="lg" p="6" sx={{ zIndex: '999'}}/>
+        <ModalCloseButton size="lg" p="6" zIndex="1"/>
         {children}
       </Center>
     </ChakraModal>