CI: remove unused rstcheck pre-commit hook

We no longer have any .rst files in this repository for it to check, so we may as well skip cloning.

This is trivial, so I'll merge it without review, so long as the CI passes.

.pre-commit-config.yaml

@@ -19,10 +19,6 @@ repos:
       # run flake8 on the diff of the merge request, otherwise it will run
       # flake8 as it would usually execute via the pre-commit hook
       entry: bash -c 'if [ -z ${CI_MERGE_REQUEST_TARGET_BRANCH_SHA} ]; then (flake8 "$@" --max-line-length 88); else (git diff $CI_MERGE_REQUEST_TARGET_BRANCH_SHA...$CI_MERGE_REQUEST_SOURCE_BRANCH_SHA | flake8 --diff --max-line-length 88); fi' --
-  - repo: https://github.com/myint/rstcheck
-    rev: 3f92957478422df87bd730abde66f089cc1ee19b  # commit where pre-commit support was added
-    hooks:
-    -   id: rstcheck
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v3.4.0
     hooks: