chore(deps): bump @mui/material from 5.15.20 to 5.15.21 (#774)

Bumps [@mui/material](https://github.com/mui/material-ui/tree/HEAD/packages/mui-material) from 5.15.20 to 5.15.21.
- [Release notes](https://github.com/mui/material-ui/releases)
- [Changelog](https://github.com/mui/material-ui/blob/v5.15.21/CHANGELOG.md)
- [Commits](https://github.com/mui/material-ui/commits/v5.15.21/packages/mui-material)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -18,7 +18,7 @@
     "@fontsource/lexend-deca": "5.0.12",
     "@fontsource/montserrat": "5.0.17",
     "@muetab/react-sortable-hoc": "^2.0.1",
-    "@mui/material": "5.15.20",
+    "@mui/material": "5.15.21",
     "@sentry/react": "^8.13.0",
     "embla-carousel-autoplay": "8.1.5",
     "embla-carousel-react": "8.1.5",