See Key:maxspeed:advisory - OpenStreetMap Wiki and Key:maxspeed:advised - OpenStreetMap Wiki
Based on my research so far maxspeed:advised is a duplicate of maxspeed:advisory with the same meaning. Which is just a pointless obstacle to data consumers and whoever would want to implement editor support for such keys (disclaimer: maybe I will be one of them)
Yes, such edit would cause objects to be edited. Yes, this mentioned obstacle is tiny and not even in top 10 000 problems for data consumers. But it is also a very easy thing to fix, with effort/benefit ratio comparable with larger issues.
So far I checked wiki, opened some notes, commented on some changesets of people who used it. For last two feedback was not large but two replies I got agreed with it.
maxspeed:advised | Keys | OpenStreetMap Taginfo maxspeed:advisory | Keys | OpenStreetMap Taginfo indicates use by Osmand - but it appears to be an Osmand bug, see List maxspeed:advisory as used in taginfo report · Issue #23223 · osmandapp/OsmAnd · GitHub - and both are used by it, see Use maxspeed:advised like maxspeed:advisory in routing.xml · Issue #2545 · osmandapp/OsmAnd · GitHub
So I am proposing to automatically migrate maxspeed:advised= to maxspeed:advisory=
Cases where both tags are present and have different values would be skipped
It would be a recurrent edit, if new elements would become eligible they would be edited.