- use `[ConditionalFact]` or `[ConditionalTheory]` instead
- in some cases test was already conditional
- move other `IsMono` checks into data sets where possible
- not reported as skipped but at least not counted as successful
nit: switch from `[ConditionalTheory]` to `[ConditionalFact]` as appropriate
- slightly more efficient since xUnit won't check for data
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