Pip update causes a local build directory creation

[PythonCoderAS]

Prior to the latest version of pip, if you did pip install ., pip would copy the current directory to a tempdir and make the build files there. However, with the merge of pypa/pip#7882, builds are done in place. This creates a build directory that basically contains a copy of the source files.

This causes flake8 to see those files and work on them as well. Now this is not good because the build directory is not in the flake8 ignore.

There are two ways to deal with this:

1. Pin pip to the previous version. Not recommended, and also the push leads to faster CI times.
2. Delete the build directory. This is the recommended option.

[jarhill0]

Let's delete the build directory (or tell linting to ignore it).

[jarhill0]

Also, I don't think this counts as critical — certainly our CI won't pass until it's fixed, but it's not like there's an active critical bug in PRAW itself. So I'm going to remove that label.