fix(deps): update starters and examples to ^1.6.19 (#27657)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

starters/gatsby-starter-blog-theme-core/package-lock.json

@@ -10,7 +10,7 @@
   },
   "license": "0BSD",
   "dependencies": {
-    "@mdx-js/react": "^1.6.18",
+    "@mdx-js/react": "^1.6.19",
     "gatsby": "^2.25.1",
     "gatsby-theme-blog-core": "^1.5.61",
     "react": "^16.12.0",

starters/gatsby-starter-blog-theme-core/package.json

@@ -4,8 +4,8 @@
   "version": "1.0.0",
   "author": "Chris Biscardi <[email protected]>",
   "dependencies": {
-    "@mdx-js/mdx": "^1.6.18",
-    "@mdx-js/react": "^1.6.18",
+    "@mdx-js/mdx": "^1.6.19",
+    "@mdx-js/react": "^1.6.19",
     "gatsby": "^2.25.1",
     "gatsby-image": "^2.4.21",
     "gatsby-plugin-manifest": "^2.5.1",