[web-php] PR #772: Use abbreviated month names

Pull Request: https://github.com/php/web-php/pull/772 Author: captn3m0 This changes the API response to always use abbreviated (en) month names. Allows for slightly more stable API clients, which don't have to worry about parsing both kinds of dates. I noticed this while working on https://github.com/endoflife-date/release-data/pull/91, where I had to write a [fallback](https://github.com/endoflife-date/release-data/pull/91/files#diff-cf71bc63cf044e0a6b6656eb67cd061b4fa9bd4bd7e0e7d4ee46c7b3bcf95d00R13-R15) where the date format changes. Ideally, this should use something non-locale based like YYYY-MM-DD, happy to file a separate PR for that if that sounds good. (At the expense of breaking the API?)