[Cleanup] Remove legacy ADAL_PYTHON_SSL_NO_VERIFY dead code

[MaddyMicrosoft]

ADAL_PYTHON_SSL_NO_VERIFY is identified in the env var analysis as confirmed unused legacy ADAL dead code in _debug.py (noted at L23 and L39). This should be removed as Azure CLI code hygiene cleanup to reduce environment-variable pollution and avoid carrying forward obsolete ADAL-era behavior

[yonzhan]

Thank you for opening this issue, we will look into it.