Don't count nucleotides 0-100 towards divergence

[corneliusroemer]

44 is very flip-floppy due to being often not properly sequenced.

We should not show it in calculation of divergence to avoid flip flops from lengthening the tree

Nextclade distance calculation should exempt 0-100 from distance calculations as well, but that's a different feature (requires an addition to virus_properties.json though - masked sites for placement)