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 }`

Signed-off-by: Rémy Coutable <remy@rymai.me>

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

Also removes the note from the development/testing.md guide

Closes #15330