Remove dependabot checks for pip dependencies

[gadomski]

Related Issue(s):

• Closes Remove dependabot for requirements-min.txt #400

Description:

I was spending a lot of time just auto-closing dependabot version bumps to requirements-min.txt (e.g. this morning: #399). The whole point behind requirements-min.txt is that we don't have to update our version files every time there's a release; for more information behind this strategy, here's a blog post I wrote. Without requirements-min.txt, and because dependabot doesn't understand setup.cfg, there really isn't much value in checking the pip package ecosystem, so I've removed it.

Also sets our other checks to weekly, we don't really need a daily cadence for this repo.

PR checklist:

• Code is formatted (run scripts/format).
• Code lints properly (run scripts/lint).
• Tests pass (run scripts/test).
• Documentation has been updated to reflect changes, if applicable.
• Changes are added to the CHANGELOG.

[pjhartzell]

Makes sense.