Updates specs to use new rails5 format.
The old format:
`get :show, { some: params }, { some: headers }`
The new format:
`get :show, params: { some: params }, headers: { some: headers }`
This new endpoint allow users to update a submodule's reference.
The MR involves adding a new operation RPC operation in gitaly-proto
(see gitlab-org/gitaly-proto!233) and change Gitaly to use this
new version (see gitlab-org/gitaly!936).
See gitlab-org/gitlab-ce!20949