Revert "chore: Add mysqlclient pip package in horizon"

This reverts commit e71f9a77e562f940a01fcdb609119665fc6055b6.
diff --git a/internal/pkg/image_repositories/build_workflow.go b/internal/pkg/image_repositories/build_workflow.go
index 937de4d..bc31282 100644
--- a/internal/pkg/image_repositories/build_workflow.go
+++ b/internal/pkg/image_repositories/build_workflow.go
@@ -34,7 +34,7 @@
 var PIP_PACKAGES map[string]string = map[string]string{
 	"cinder":        "purestorage",
 	"glance":        "glance_store[cinder]",
-	"horizon":       "mysqlclient git+https://github.com/openstack/designate-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/heat-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/ironic-ui.git@stable/${{ matrix.release }} git+https://github.com/openstack/magnum-ui.git@stable/${{ matrix.release }} git+https://github.com/openstack/neutron-vpnaas-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/octavia-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/senlin-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/monasca-ui.git@stable/${{ matrix.release }}",
+	"horizon":       "git+https://github.com/openstack/designate-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/heat-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/ironic-ui.git@stable/${{ matrix.release }} git+https://github.com/openstack/magnum-ui.git@stable/${{ matrix.release }} git+https://github.com/openstack/neutron-vpnaas-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/octavia-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/senlin-dashboard.git@stable/${{ matrix.release }} git+https://github.com/openstack/monasca-ui.git@stable/${{ matrix.release }}",
 	"ironic":        "python-dracclient sushy",
 	"magnum":        "magnum-cluster-api==0.2.7",
 	"monasca-agent": "libvirt-python python-glanceclient python-neutronclient python-novaclient py3nvml",