Bump apollo-server from 2.6.9 to 2.14.2 in /examples/twitter

Bumps [apollo-server](https://github.com/apollographql/apollo-server) from 2.6.9 to 2.14.2.
- [Release notes](https://github.com/apollographql/apollo-server/releases)
- [Changelog](https://github.com/apollographql/apollo-server/blob/master/CHANGELOG.md)
- [Commits](https://github.com/apollographql/apollo-server/compare/apollo-server@2.6.9...apollo-server@2.14.2)

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