Bump @mui/material from 5.14.14 to 5.15.21 in /src

Bumps [@mui/material](https://github.com/mui/material-ui/tree/HEAD/packages/mui-material) from 5.14.14 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-minor
...

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

src/package.json

@@ -4,7 +4,7 @@
     "private": true,
     "dependencies": {
         "@iobroker/adapter-react-v5": "^4.9.10",
-        "@mui/material": "5.14.14",
+        "@mui/material": "5.15.21",
         "@mui/icons-material": "^5.15.21",
         "@mui/styles": "5.14.14",
         "babel-eslint": "^10.1.0",