Annotations removing can hang GUI for some time

Scenario to reproduce:

1. Open "data/samples/FASTA/human_T1.fa".
2. Search restriction sites: select all enzymes with length more or equal 10.
   Expected state: there are many groups with many annotation in each.
3. Click {Global automatic annotation highlighting -> Hide restriction sites}

   button on the main toolbar.
   Current state: GUI hangs for some time.

Annotations removing should be improved.