Bump graphql-playground-react from 1.7.20 to 1.7.28 in /parse-server

Bumps [graphql-playground-react](https://github.com/graphcool/graphql-playground) from 1.7.20 to 1.7.28.
- [Release notes](https://github.com/graphcool/graphql-playground/releases)
- [Commits](https://github.com/graphcool/graphql-playground/compare/graphql-playground-middleware-lambda@1.7.20...graphql-playground-react@1.7.28)

---
updated-dependencies:
- dependency-name: graphql-playground-react
  dependency-type: indirect
...

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