This was overriding using a nonexistant jenkins var

Jenkins wasn't updated when this code was changed, so THEME_DIRS
was always null.  We're now going to just set the correct directories
in the internal sandbox config which removes the need for this var
setting here.

util/jenkins/ansible-provision.sh

@@ -187,7 +187,6 @@ edx_ansible_source_repo: ${configuration_source_repo}
 edx_platform_repo: ${edx_platform_repo}
 
 EDXAPP_PLATFORM_NAME: $sandbox_platform_name
-EDXAPP_COMPREHENSIVE_THEME_DIRS: $edxapp_comprehensive_theme_dirs
 
 EDXAPP_STATIC_URL_BASE: $static_url_base
 EDXAPP_LMS_NGINX_PORT: 80