Enable scenario tests for DevVersions UB leg

[mthalman]

Execution of the scenario tests needed to be disabled for the DevVersions UB leg via this logic. The DevVersions leg uses unofficial build versioning which causes various issues with the tests that are described in dotnet/installer#19222 (comment). These issues need to be resolved so that the tests can be enabled for this build leg.

[mthalman]

This change will also need to be reverted: dotnet/sdk#40860