Bump @mui/icons-material from 5.15.20 to 5.15.21 in /webui

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

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

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

webui/package-lock.json

@@ -11,7 +11,7 @@
         "@emotion/react": "^11.11.4",
         "@emotion/styled": "^11.11.5",
         "@fontsource/inter": "^5.0.18",
-        "@mui/icons-material": "^5.15.20",
+        "@mui/icons-material": "^5.15.21",
         "@mui/material": "^5.15.20",
         "i18next": "^23.11.5",
         "i18next-browser-languagedetector": "^8.0.0",
@@ -1137,9 +1137,9 @@
       }
     },
     "node_modules/@mui/icons-material": {
-      "version": "5.15.20",
-      "resolved": "https://registry.npmjs.org/@mui/icons-material/-/icons-material-5.15.20.tgz",
-      "integrity": "sha512-oGcKmCuHaYbAAoLN67WKSXtHmEgyWcJToT1uRtmPyxMj9N5uqwc/mRtEnst4Wj/eGr+zYH2FiZQ79v9k7kSk1Q==",
+      "version": "5.15.21",
+      "resolved": "https://registry.npmjs.org/@mui/icons-material/-/icons-material-5.15.21.tgz",
+      "integrity": "sha512-yqkq1MbdkmX5ZHyvZTBuAaA6RkvoqkoAgwBSx9Oh0L0jAfj9T/Ih/NhMNjkl8PWVSonjfDUkKroBnjRyo/1M9Q==",
       "dependencies": {
         "@babel/runtime": "^7.23.9"
       },