[pickers] Remove PickersDay and promote PickerDay2 as a replacement

docs/data/date-pickers/date-calendar/WeekPicker.js

@@ -13,6 +13,7 @@ const CustomPickersDay = styled(PickersDay, {
   shouldForwardProp: (prop) => prop !== 'isSelected' && prop !== 'isHovered',
 })(({ theme, isSelected, isHovered, day }) => ({
   borderRadius: 0,
+  display: 'flex',
   ...(isSelected && {
     backgroundColor: theme.palette.primary.main,
     color: theme.palette.primary.contrastText,

docs/data/date-pickers/date-calendar/WeekPicker.tsx

@@ -18,6 +18,7 @@ const CustomPickersDay = styled(PickersDay, {
   shouldForwardProp: (prop) => prop !== 'isSelected' && prop !== 'isHovered',
 })<CustomPickerDayProps>(({ theme, isSelected, isHovered, day }) => ({
   borderRadius: 0,
+  display: 'flex',
   ...(isSelected && {
     backgroundColor: theme.palette.primary.main,
     color: theme.palette.primary.contrastText,

packages/x-date-pickers/src/PickersDay/PickersDay.tsx

@@ -53,6 +53,7 @@ const useUtilityClasses = (
 
 const styleArg = ({ theme }: { theme: Theme }) => ({
   ...theme.typography.caption,
+  display: 'block',
   width: DAY_SIZE,
   height: DAY_SIZE,
   borderRadius: '50%',