always run git-hooks installation script

[jashandeep-sohi]

To keep .pre-commit-config.yaml in sync when all hooks are disabled

#1748

[sandydoo]

Thanks for tacking this, @jashandeep-sohi.

I'm worried that we'll get a lot of complaints from users asking why git-hooks:install is running and why they now have a .pre-commit-hooks.yaml file in their repo when they haven't enabled the integration.

It might make sense for now to add a few lines to enterShell that: tests for .pre-commit-hooks.yaml, looks for "# This file was generated by git-hooks.nix" (or "pre-commit-hooks.nix"), and removes it.

It'd be nice to have some type of "uninstall" task that wouldn't be logged if it didn't run. But that seems out of scope for now.