Bump @mui/material from 5.15.15 to 5.15.16 in /frontend

Bumps [@mui/material](https://github.com/mui/material-ui/tree/HEAD/packages/mui-material) from 5.15.15 to 5.15.16.
- [Release notes](https://github.com/mui/material-ui/releases)
- [Changelog](https://github.com/mui/material-ui/blob/v5.15.16/CHANGELOG.md)
- [Commits](https://github.com/mui/material-ui/commits/v5.15.16/packages/mui-material)

---
updated-dependencies:
- dependency-name: "@mui/material"
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

frontend/package.json

@@ -42,7 +42,7 @@
     "@babel/runtime": "^7.24.5",
     "@mui/icons-material": "^5.15.15",
     "@mui/lab": "5.0.0-alpha.170",
-    "@mui/material": "^5.15.15",
+    "@mui/material": "^5.15.16",
     "@mui/styled-engine-sc": "^5.14.12",
     "immutable": "^4.3.5",
     "prop-types": "15.8.1",