companion of GNSSRO super refraction check 3119

[hailingz]

Description

This PR adds a new variables "srCheckImpp" to the "TestReference" group for the obs file. The generated Diag flag should match "TestReference/srCheckImpp" when running the ctest "test_ufo_gnssro_super_refraction_check".

required for https://github.com/JCSDA-internal/ufo/pull/3119

Issue(s) addressed

N/A

Dependencies

N/A

List the other PRs that this PR is dependent on: N/A

Impact

N/A

Checklist

• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [x] I have run the unit tests before creating the PR