Remove tool group component file

[jarmoza]

Now that assessment tool categories will be dynamically created and automatically grouped (per category), we no longer need the annot-tool-group component.

It's possible that some of its code may be reused for the new functionality.

This task is to remove the old component file annot-tool-group.vue from the annotation tool repo once the new feature is in place - see #228 .

[github-actions]

We want to keep our issues up to date and active. This issue hasn't seen any activity in the last 30 days.
We have applied the stale-issue label to indicate that this issue should be reviewed again and then either prioritized or closed.

[jarmoza]

Closed by #383