fix(pre-commit): pin version of node used for running markdownlint

For whatever reason, markdownlint-cli2 and node 23.0 don't like each other and so we are getting failed jobs. For the moment work around this by pinning the node language version.

Example failing job: https://gitlab.developers.cam.ac.uk/uis/devops/docs/guidebook/-/jobs/1785816

assigned to @rjw57

mentioned in issue uis/devops/continuous-delivery/ci-templates#85 (moved)

approved this merge request

enabled an automatic merge when all merge checks for 92c2dbdc pass

merged

mentioned in commit 9bf48882

mentioned in issue #272

mentioned in issue #271 (closed)