fix(deps): replace dependency @material-ui/core with @mui/material 5.0.0

Author: renovate[bot]

package.json

@@ -42,7 +42,7 @@
   },
   "dependencies": {
     "@emotion/core": "11.0.0",
-    "@material-ui/core": "4.12.4",
+    "@mui/material": "5.0.0",
     "@travi/brand": "1.0.0",
     "@travi/travi.org-theme-components": "1.2.0",
     "gatsby": "4.25.6",