API: locales service returns different structure per repo

[pascalchevrel]

https://transvision-beta.mozfr.org/api/v1/locales/central/
returns a list with indexed values such as:

{
    "0": "ar",
    "1": "ast",
    "2": "cs"
}

While gaia returns a list without indices:
https://transvision-beta.mozfr.org/api/v1/locales/gaia/

[
    "af",
    "ar",
    "as",
    "ast"
]

This is a bug, we should return the same data structure, the simple one without indices seems more logical to me.