[CHORE] Update GUI Frontend to v5.15.21

[renovate[bot]]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@mui/icons-material (source)	5.15.20 -> 5.15.21
@mui/material (source)	5.15.20 -> 5.15.21

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Release Notes

mui/material-ui (@​mui/icons-material)

### [`v5.15.21`](https://togithub.com/mui/material-ui/releases/tag/v5.15.21) *Jun 28, 2024* A big thanks to the 7 contributors who made this release possible. ##### `@mui/material@5.15.21` - \[Autocomplete] Fix renderOption props type ([@​DiegoAndai](https://togithub.com/DiegoAndai)) ([#​42709](https://togithub.com/mui/material-ui/issues/42709)) [@​DiegoAndai](https://togithub.com/DiegoAndai) - \[Stepper] Generate class for `nonLinear` prop ([@​alexismo](https://togithub.com/alexismo)) ([#​42677](https://togithub.com/mui/material-ui/issues/42677)) [@​alexismo](https://togithub.com/alexismo) ##### Docs - Use new email for sponsoring [@​oliviertassinari](https://togithub.com/oliviertassinari) - Fix 301 links ([@​alexfauquette](https://togithub.com/alexfauquette)) ([#​42700](https://togithub.com/mui/material-ui/issues/42700)) [@​alexfauquette](https://togithub.com/alexfauquette) - \[material-ui]\[Select] Fix the `SelectAutoWidth` demo menu item value ([@​Danielkhakbaz](https://togithub.com/Danielkhakbaz)) ([#​42696](https://togithub.com/mui/material-ui/issues/42696)) [@​Danielkhakbaz](https://togithub.com/Danielkhakbaz) - \[material-ui]\[Autocomplete] Fix more React 18.3 key spread warnings in demos ([#​42766](https://togithub.com/mui/material-ui/issues/42766)) [@​wbt](https://togithub.com/wbt) - \[material-ui] Fix sign in side image ([#​42708](https://togithub.com/mui/material-ui/issues/42708)) [@​zanivan](https://togithub.com/zanivan) - \[website] Add Ale to team ([#​42769](https://togithub.com/mui/material-ui/issues/42769)) [@​alelthomas](https://togithub.com/alelthomas) ##### Core - \[core] Cherry pick pnpm updates ([#​42763](https://togithub.com/mui/material-ui/issues/42763)) [@​DiegoAndai](https://togithub.com/DiegoAndai) - \[website] Add Armin to the team members ([@​arminmeh](https://togithub.com/arminmeh)) ([#​42681](https://togithub.com/mui/material-ui/issues/42681)) [@​arminmeh](https://togithub.com/arminmeh) - \[website] Open Staff Engineer role for Pigment CSS ([@​mnajdova](https://togithub.com/mnajdova)) ([#​42669](https://togithub.com/mui/material-ui/issues/42669)) [@​mnajdova](https://togithub.com/mnajdova) All contributors of this release in alphabetical order: [@​alexfauquette](https://togithub.com/alexfauquette), [@​alexismo](https://togithub.com/alexismo), [@​arminmeh](https://togithub.com/arminmeh), [@​Danielkhakbaz](https://togithub.com/Danielkhakbaz), [@​DiegoAndai](https://togithub.com/DiegoAndai), [@​mnajdova](https://togithub.com/mnajdova), [@​oliviertassinari](https://togithub.com/oliviertassinari)

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