fix: update dependency theme-ui to ^0.2.31 (#16436)

Author: renovate[bot]

themes/gatsby-theme-blog/package.json

@@ -43,7 +43,7 @@
     "react-helmet": "^5.2.1",
     "react-switch": "^5.0.1",
     "remark-slug": "^5.1.2",
-    "theme-ui": "^0.2.29",
+    "theme-ui": "^0.2.31",
     "typeface-merriweather": "0.0.72",
     "typeface-montserrat": "0.0.75",
     "typography-theme-wordpress-2016": "^0.16.19"

themes/gatsby-theme-notes/package.json

@@ -44,6 +44,6 @@
     "gatsby-source-filesystem": "^2.1.8",
     "is-present": "^1.0.0",
     "react-feather": "^1.1.6",
-    "theme-ui": "^0.2.29"
+    "theme-ui": "^0.2.31"
   }
 }