Bump @mui/x-data-grid from 6.12.1 to 6.15.0 in /webapp

Bumps [@mui/x-data-grid](https://github.com/mui/mui-x/tree/HEAD/packages/grid/x-data-grid) from 6.12.1 to 6.15.0.
- [Release notes](https://github.com/mui/mui-x/releases)
- [Changelog](https://github.com/mui/mui-x/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mui/mui-x/commits/v6.15.0/packages/grid/x-data-grid)

---
updated-dependencies:
- dependency-name: "@mui/x-data-grid"
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

webapp/package.json

@@ -8,7 +8,7 @@
     "@fontsource/roboto": "^5.0.1",
     "@mui/icons-material": "^5.11.16",
     "@mui/material": "^5.12.0",
-    "@mui/x-data-grid": "^6.5.0",
+    "@mui/x-data-grid": "^6.15.0",
     "@reduxjs/toolkit": "^1.9.3",
     "@testing-library/jest-dom": "^5.16.5",
     "@testing-library/react": "^14.0.0",