Update MUI date picker to try and obtain the UTC functionality

Per https://mui.com/blog/mui-x-v6/#decoupling-versions-from-mui-core, the
version of MUI X is now decoupled from MUI core so this should work even when
our MUI remains at 5.

Migration:
- https://mui.com/x/migration/migration-pickers-v5/
- https://mui.com/x/migration/migration-tree-view-v6/

web/packages/new/package.json

@@ -6,7 +6,7 @@
         "@/base": "*",
         "@/utils": "*",
         "@ente/shared": "*",
-        "@mui/x-date-pickers": "^5.0.20",
+        "@mui/x-date-pickers": "^7.12.0",
         "dayjs": "^1.11.12",
         "formik": "^2.4",
         "idb": "^8",