Extra annotation rows appear when removing and recreating group in example project

1. Load the Jalview exampleFile2_7.jvp project
2. Select the Fe2S2 Representatives
3. Select Annotations->Automatic Annotations->Apply to All Groups
4. Click on one of the groups to select it.
5. Use the menus or SHIFT-CTRL-G to remove the group, then without changing the selection create the group again.

Bug: instead of seeing a group associated annotation row disappear and reappear each time, additional annotation rows are created.

Inspection didn't reveal any straightforward fix - the additional rows are annotation objects which seem to share the same Annotation[] array reference - so changing the group membership causes all the duplicate rows to update. However, only one of those rows has a non-null groupRef - suggesting the 'remove Group' operation isn't properly deleting the group associated annotation row from the alignment. JAL-3107 seems to have brought this bug to the fore.