Fix: removal deprecated module

[JacobCoffee]

warehouse/warehouse/forklift/legacy.py

Line 10 in cb0d5bc

from cgi import FieldStorage

cgi was removed in 3.13 stdlib but we migrated to 3.14

https://docs.python.org/3/library/cgi.html

[miketheman]

We get cgi's successor legacy-cgi via webob:
https://github.com/Pylons/webob/blob/39d5af3c797e7b867f152c2e8c979de42d029403/setup.py#L56-L58