Temporarily use forked version of mlc

Use forked version of markdown-link-check until
https://github.com/gaurav-nelson/github-action-markdown-link-check/pull/126
lands.

Signed-off-by: Thane Thomson <connect@thanethomson.com>

.github/workflows/markdown-links.yml

@@ -12,6 +12,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: gaurav-nelson/github-action-markdown-link-check@1.0.13
+      - uses: thanethomson/github-action-markdown-link-check@611438d456810f86e2053576f7e62a433da10e0e
         with:
           check-modified-files-only: 'yes'