fix(deps): update material-ui monorepo to v5.15.21

Author: renovate[bot]

autotest/IntegTester/front-end/package-lock.json

@@ -9,7 +9,7 @@
   "dependencies": {
     "@emotion/react": "11.11.4",
     "@emotion/styled": "11.11.5",
-    "@mui/material": "5.15.16",
+    "@mui/material": "5.15.21",
     "axios": "1.6.8",
     "babel-polyfill": "6.26.0",
     "jss": "10.10.0",

autotest/IntegTester/front-end/package.json

@@ -50,9 +50,9 @@
     "@emotion/styled": "11.11.5",
     "@fontsource/material-icons": "4.5.4",
     "@fontsource/roboto": "4.5.8",
-    "@mui/icons-material": "5.15.16",
+    "@mui/icons-material": "5.15.21",
     "@mui/lab": "5.0.0-alpha.170",
-    "@mui/material": "5.15.16",
+    "@mui/material": "5.15.21",
     "@mui/x-date-pickers": "5.0.20",
     "@mui/x-tree-view": "6.17.0",
     "@openequella/rest-api-client": "file:../oeq-ts-rest-api",