#578 Fix occurrences of 'have been' to 'has been'

A: API
Related to the REST API A: Backend
Code running on the server A: Federation
Stuff related to Federation A: Front-End
Related to the front-end A: I18N
Translations, and related code A: Meta
More about project management or code than the project itself A: Security Build
The building, or installation process of Plume C: Bug
Something isn't working C: Discussion
We need to talk C: Enhancement
New feature or request C: Feature
This is a new feature Compatibility
Compatibility with different browsers, readers and OS Dependency
Related to an external package that Plume uses Design
UI/UX related issues and PRs Documentation Good first issue
Good for newcomers Help welcome
Extra attention is needed Mobile
Issues affecting only mobile UX Rendering
How elements're rendered out for the end user S: Blocked
Something else needs to be fixed first S: Duplicate
This issue or pull request already exists S: Incomplete
This PR is not complete yet S: Instance specific
Issues concern a limited number of instances S: Invalid
This doesn't seem right S: Needs Voting/Discussion
Need to be discussed by the community (on Loomio) S: Ready for review
This PR is ready to be reviewed Suggestion
Proposed ideas worth considering S: Voted on Loomio
This is issue has been created after a vote on Loomio S: Wontfix
This will not be worked on