Adapt components to new mui & nextjs versions

components/stats/kat-stats.js

@@ -2,13 +2,13 @@ import PropTypes from 'prop-types'
 import Card from '@mui/material/Card'
 import CardContent from '@mui/material/CardContent'
 import Typography from '@mui/material/Typography'
-import Grid from '@mui/material/Grid'
+import Grid from '@mui/material/Unstable_Grid2'
 
 import TraductionsStats from './traductions-stats'
 
 export default function KatStats({emoji, value, total}) {
   return (
-    <Grid item xs={12} md={2}>
+    <Grid xs={12} md={2}>
       <Card variant='outlined'>
         <CardContent>
           <Typography align='center' variant='h6'>