fix(deps): update dependency theme-ui to ^0.16.0 (#38317)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

e2e-tests/mdx/package.json

@@ -19,7 +19,7 @@
     "react-dom": "^18.2.0",
     "rehype-slug": "^5.1.0",
     "remark-gfm": "^3.0.1",
-    "theme-ui": "^0.15.7"
+    "theme-ui": "^0.16.0"
   },
   "keywords": [
     "gatsby"