Reverting changes to use of mysign in corners.py

[fmalatino]

Description
Regarding fixes to orchestration for unused variables, this change of mysign to an external variable is no longer necessary, and so to preserve the original state of the python source this change is being reverted.

How Has This Been Tested?
Tested via CI triggering translate tests across dependent repositories

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
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included