Use latest simulator by not specifying the OS version

Summary:Appetize asked for this so they can better support us, since they will usually have more simulators available for the latest versions.
Closes facebook#7061

Differential Revision: D3196110

Pulled By: mkonicek

fb-gh-sync-id: 2406ab6e1ee352f0148957e851d7f483a2182f90
fbshipit-source-id: 2406ab6e1ee352f0148957e851d7f483a2182f90

[0.24.1] Bump version numbers

[0.24.0] Bump version numbers

[0.25.0-rc] Bump version numbers

[0.24.0-rc5] Bump version numbers

[0.24.0-rc4] Bump version numbers

[0.24.0-rc3] Bump version numbers

[0.23.1] Bump version numbers

[0.24.0-rc2] Bump version numbers

[0.23.0] Bump version numbers