fix: Fix type for Webhook

[silversonicaxel]

as this is the response I receive

const mockAbstractWebhookResponseMergedIntoMaster = {
  createdAt: '2020-07-29T09:55:04Z',
  event: 'branch.statusUpdated',
  data: {
    changes: {
      status: ['wip', 'merged']
    },
    object: {
      createdAt: '2020-07-29T09:52:44Z',
      description: '',
      divergedFromBranchId: '',
      head: 'XXX',
      id: 'XXX',
      mergeSha: 'XXX',
      mergedIntoBranchId: 'master',
      name: 'test-2',
      objectType: 'branch',
      parent: 'master',
      projectId: 'XXX',
      startedAtSha: 'XXX',
      status: 'merged',
      updatedAt: '2020-07-29T09:54:46Z',
      user: {
        avatarUrl:
          'https://www.gravatar.com/avatar/XXX?r=pg&s=160&d=404',
        createdAt: '2019-08-22T06:51:02Z',
        id: 'XXX',
        name: 'XXX',
        objectType: 'user',
        updatedAt: '2019-08-22T06:51:02Z',
        username: 'XXX'
      }
    }
  }
}

export default mockAbstractWebhookResponseMergedIntoMaster

I think Webhook type should be updated