Remove redundant passenv from tox

This env var is no longer needed on macos - and regardless of that, it
actually doesn't get passed through as macos does not pass through DYLD_
vars (part of their 'system integrity protection')

tox.ini

@@ -12,7 +12,6 @@ package = wheel
 wheel_build_env = .pkg
 constrain_package_deps = true
 use_frozen_constraints = true
-passenv = DYLD_LIBRARY_PATH
 # TODO: Remove SQLALCHEMY_SILENCE_UBER_WARNINGwhen Flask-Admin is compatible with SQLAlchemy>=2.0.0
 setenv =
     SQLALCHEMY_SILENCE_UBER_WARNING = 1