chore: don't depend on pip

[xmatthias]

packages shouldn't usually depend on pip unless they actually need it (import from it etc).

currently - when installing ta-lib in an uv venv (which usually doensn't come with pip) - pip is installed as dependency of ta-lib.

to reproduce:

uv venv
. .venv/bin/activate
uv pip install ta-lib
uv pip show pip

which outputs:

Name: pip
Version: 25.2
Location: /home/xmatt/devel/.venv/lib/python3.13/site-packages
Requires:
Required-by: ta-lib    <-- pip is only installed due to ta-lib

if dependencies of pip were required (there ain't any) - then these should be listed instead.