chore(deps): bump @mui/system from 5.15.15 to 5.15.20 (#1362)

Bumps [@mui/system](https://github.com/mui/material-ui/tree/HEAD/packages/mui-system) from 5.15.15 to 5.15.20.
- [Release notes](https://github.com/mui/material-ui/releases)
- [Changelog](https://github.com/mui/material-ui/blob/v5.15.20/CHANGELOG.md)
- [Commits](https://github.com/mui/material-ui/commits/v5.15.20/packages/mui-system)

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

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