Treat a 100 percent ramp in a versioning assignment rule as unramped

[antlai-temporal]

Is your feature request related to a problem? Please describe. Customers are getting confused when they cannot set a 100% ramp, and they need a special case Describe the solution you'd like

Treat a 100% ramp in an assignment versioning rule as un-ramped. This depends on server changes in https://github.com/temporalio/temporal/pull/6409