Revert "Set GLOBAL_VENV=false to fix broken gate jobs"

This reverts commit d84b96d294439c6ad70794da94c5f69c8853e9b1.

Reason for revert: OVS jobs with GLOBAL_VENV=True are being fixed
with [1]. dynamic-routing jobs already fixed with os-ken latest release[2].

[1] https://review.opendev.org/c/openstack/devstack/+/892848
[2] https://review.opendev.org/c/openstack/releases/+/892214

Depends-On: https://review.opendev.org/c/openstack/devstack/+/892848
Related-bug: #2031415
Related-bug: #2031526
Change-Id: Ifae116a443ba500deb4cf01fdc92c87eb83d7582
2 files changed