Remove unused Options.HasDeleteAllButN property.
Remove unused Options.HasDeleteAllButN property.

The last reference was removed in revision
3b70f99722ed03dfe4e6af0d2327e731c581414f.

mnaiman/duplicati,mnaiman/duplicati,duplicati/duplicati,duplicati/duplicati,mnaiman/duplicati,duplicati/duplicati,duplicati/duplicati,duplicati/duplicati,mnaiman/duplicati,mnaiman/duplicati