Remove unused language choices
## Problem
There are several languages currently available in GitLab as a user preference, but their translation levels are between 0% and 2%. This kind of a "false" choice creates a disappointing experience for the user, as there is pretty much no change in the UI once it is selected.
## Solution
We will remove these choices from the UI until they reach at least 10% translated strings.
### TODO
- https://gitlab.com/gitlab-org/gitlab/-/merge_requests/38312
- [x] Make [the list](#the-list) of languages not available in the UI
- [x] Update the [documentation](https://docs.gitlab.com/ee/development/i18n/externalization.html#adding-a-new-language) with the information that languages with less than 2% of translations won't be available in the UI.
### The List
These languages have 2% translation levels or less and are currently available in the UI (the numbers in the parenthesis are the current number of users with this selection and that number represented as a % of the total number of users):
* Filipino (2 - 0.00%)
* Polish (1,435 - 0.03%)
* Dutch (472 - 0.01%)
* Indonesian (930 - 0.02%)
* Czech (378 - 0.01%)
* Bulgarian (37 - 0.00%)
* Esperanto (25 - 0.00%)
* Galician (27 - 0.00%)
issue