Remove trailing comma from test/tsconfig.json

[Stasi V]

Using TypeScript Auto Compiler in VSCode throws an error:

node_modules/fastq/test/tsconfig.json. Error: Unexpected token } in JSON at position 114

[Matteo Collina]

Would you like to send a Pull Request to address this issue? Remember to add unit tests.

[Stasi V]

#20

[Matteo Collina]

Thanks!