Regression from MDL-77991 here: https://github.com/moodle/moodle/commit/a4b3b0d044371ff15946d3a01076a8b51dc14330#diff-8f7313d16bc4fca693b74b1bd628d7bef23aa7de653886e684f4c82dcba2cd31R78 - we are effectively hardcoding the {[aria-label}} of all these drop down elements

They are used four times on the gradebook page:

1. User search
2. Group search
3. User filter by initials
4. Collapsed columns

Fix the label of each so that it related to it's content (instead of "Select a group")