build(deps): Bump @mui/private-theming from 5.15.6 to 5.15.7

Bumps [@mui/private-theming](https://github.com/mui/material-ui/tree/HEAD/packages/mui-private-theming) from 5.15.6 to 5.15.7.
- [Release notes](https://github.com/mui/material-ui/releases)
- [Changelog](https://github.com/mui/material-ui/blob/master/CHANGELOG.md)
- [Commits](https://github.com/mui/material-ui/commits/v5.15.7/packages/mui-private-theming)

---
updated-dependencies:
- dependency-name: "@mui/private-theming"
  dependency-type: indirect
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>