Incorrect Locale allocation causes English to show in the UI

The main Jira Cloud UI uses browser language (Accept-Language) to apply UI language settings. However, some parts of the Jira Product use the user settings language as their source of truth. This is currently set by default to English, which results in users seeing side menus and some other text in English.

Our locale application needs to be updated as the wrong source of truth is being referenced and English should be removed as a default for all customers, and replaced with the browser language (Accept-Language) setting as a default