Remove locale prefix from rest routes

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Doc PR        | To come

I think the ``_locale`` prefix should (or not) be set globally when importing the rest.xml file.

I personnaly have one domain per locale so I don't need to prefix these routes.

If this PR is accepted, I will add the corresponding documentation.