update AnnounceAddress docstring
update AnnounceAddress docstring

mention that the host's address will be updated if the annoucne is successful.

ChrisSchinnerl/Sia,ericflo/Sia,ChrisSchinnerl/Sia,mtlynch/Sia,ericflo/Sia,MrStrong/Sia,NebulousLabs/Sia,mharkus/Sia,NebulousLabs/Sia,MrStrong/Sia,mharkus/Sia,mtlynch/Sia