Pre-commit: Fix the `jsonnet-lint` hook

What

Add a workaround to make the jsonnet-lint pre-commit-hook working correctly

Why

The jsonnet-link hook is broken, see https://github.com/google/go-jsonnet/issues/591

How

• Add -J grafazos/vendor, so that jsonnet-lint knows about Grafonnet
• Modify the pre-commit-hook so that jsonnet-lint is applied multiple times to a single file, instead of everything at once (which fails because of a bug in the tool).

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR