Move @types/sinon to prod dependencies

[claabs]

Building with Typescript on a project that doesn't already use sinon throws this error:

node_modules/aws-sdk-client-mock/dist/types/awsClientStub.d.ts:2:41 - error TS7016: Could not find a declaration file for module 'sinon'. '<my-project>/node_modules/sinon/lib/sinon.js' implicitly has an 'any' type.
  Try `npm install @types/sinon` if it exists or add a new declaration (.d.ts) file containing `declare module 'sinon';`

2 import { SinonSpyCall, SinonStub } from 'sinon';
                                          ~~~~~~~

The Typescript handbook recommends that any exported type that has a dependency on a package should be in the dependencies rather than devDependencies. Moving @types/sinon to the dependencies would solve this issue.

[m-radzikowski]

Thank you for the link to the docs, didn't know about it. Should be OK now in v0.5.0.