Bump @apollographql/graphql-playground-html from 1.6.6 to 1.6.20

Bumps [@apollographql/graphql-playground-html](https://github.com/graphcool/graphql-playground) from 1.6.6 to 1.6.20.
- [Release notes](https://github.com/graphcool/graphql-playground/releases)
- [Commits](https://github.com/graphcool/graphql-playground/commits)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

package-lock.json

@@ -19,7 +19,7 @@
   ],
   "license": "BSD-3-Clause",
   "dependencies": {
-    "@apollographql/graphql-playground-html": "1.6.6",
+    "@apollographql/graphql-playground-html": "1.6.20",
     "@parse/fs-files-adapter": "1.0.1",
     "@parse/push-adapter": "3.0.0",
     "@parse/s3-files-adapter": "1.2.1",