ci: Remove PACE_TEST_N_THRESHOLD_SAMPLES in translate tests

[romanc]

Description

Don't set PACE_TEST_N_THRESHOLD_SAMPLES in translate tests anymore since the environment variable was renamed in PR NOAA-GFDL/NDSL#134 and the default changed to match the currently configured behavior.

Now that develop of PyFV3 tracks develop of NDSL, we can do this change without waiting for a release of NDSL (which is incoming anyway).

How Has This Been Tested?

By running the CI.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas: N/A
• I have made corresponding changes to the documentation: N/A
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included: N/A
• Targeted model if this changed was triggered by a model need/shortcoming: N/A

[romanc]

@FlorianDeconinck / @fmalatino pinging you here since I don't have the rights to assign reviewers in the PyFV3 repo.

[FlorianDeconinck]

🧹