Don't use git:// URLs in pre-commit hooks

Unauthenticated `git://` URLs are no longer supported by GitHub:

```
    fatal: remote error: 
      The unauthenticated git protocol on port 9418 is no longer supported.
    Please see https://github.blog/2021-09-01-improving-git-protocol-security-github/ for more information.
```

.pre-commit-config.yaml

@@ -53,7 +53,7 @@ repos:
   - id: flake8
     exclude: "^docs/"
 
-- repo: git://github.com/Lucas-C/pre-commit-hooks-markup
+- repo: https://github.com/Lucas-C/pre-commit-hooks-markup
   rev: v1.0.1
   hooks:
   - id: rst-linter