IN-894 Remove Pipfile.lock

Why these changes are being introduced:
* The Pipfile.lock shouldn't be included in the template as it risks
pinning standard dependencies to outdated versions; unintentionally committed

How this addresses that need:
* Remove Pipfile.lock

Side effects of this change:
* None

Relevant ticket(s):
* https://mitlibraries.atlassian.net/browse/IN-894

Author: jonavellecuerdo