Syntax error: Remove trailing comma after rest arg

[cspotcode]

There's a trailing comma after a rest parameter. This won't be allowed in TypeScript 2.9, so as to match the ECMAScript spec.

https://github.com/apollographql/graphql-tools/blob/master/src/stitching/delegateToSchema.ts#L35

Blog post where they announce the change: https://blogs.msdn.microsoft.com/typescript/2018/05/16/announcing-typescript-2-9-rc/
Github issue for the change: microsoft/TypeScript#22262

It's very minor, I know, but I discovered it because recast attempts to parse the graphql codebase in its unit tests, and this file was failing to parse. And if you ever want to upgrade to TS2.9 you'll have to remove it anyway.

[JakeDawkins]

We'd be willing to accept this PR if (or anyone else) could open it!

[yaacovCR]

Closing stale issue