Remove pre-commit configuration
This didn't come with copyright and licensing information, making the REUSE check regress. From the commit message, it seems it might have been copied or derived from elsewhere: if that's the case, then we need to preserve its original copyright and licensing information.
I am also not comfortable about encouraging g-d-p committers to download and execute code outside our control from Github. If we want to have lint checks for whitespace, Markdown and flake8 issues, we should start by defining them like our other lint checks.
This partially reverts commit b87864ca "add pre-commit adapted from OSGeo/grass".
/cc @detiste-guest FYI. I don't want to just revert your changes without letting you know, but I also don't want to be violating someone else's copyright.