fix: switch py38.txt to releases/quince.txt (#141)

Switch to a more permanent requirements file
for codejail sandbox, so py38.txt can be removed.

playbooks/roles/edxapp/defaults/main.yml

@@ -1761,7 +1761,7 @@ base_requirements_file:   "{{ edxapp_code_dir }}/requirements/edx/base.txt"
 django_requirements_file:   "{{ edxapp_code_dir }}/requirements/edx/django.txt"
 openstack_requirements_file: "{{ edxapp_code_dir }}/requirements/edx/openstack.txt"
 
-sandbox_base_requirements:  "{{ edxapp_code_dir }}/requirements/edx-sandbox/py38.txt"
+sandbox_base_requirements:  "{{ edxapp_code_dir }}/requirements/edx-sandbox/releases/quince.txt"
 
 # The Python requirements files in the order they should be installed.  This order should
 # match the order of PYTHON_REQ_FILES in edx-platform/pavelib/prereqs.py.