Minor text fix for contributing.md path in prepare script

Overview

When new contributors run npm i as part of onboarding, they get a handy warning to install pre-commit.

This MR makes a very minor text fix for the path of the contributing.md doc:

pre-commit is not installed, see contributing.md

How to Test

If pre-commit is already installed, one way you can simulate failure is:

git config --add core.hooksPath .broken

Then run npm i. Since pre-commit needs a clear hooks path, you should see the script error message (after a warning).

Clear the git config again using:

git config --unset core.hooksPath