Use 1 thread to avoid rate limits

Author: urfeex

.github/workflows/check_links.yml

@@ -31,6 +31,7 @@ jobs:
             --max-cache-age 2d
             './**/*.md' './**/*.html' './**/*.rst' './**/*.cpp' './**/*.h' './**/*.py'
             --exclude '^http://192\.168\.56\.101'
+            --threads 1
       - name: Save lychee cache
         uses: actions/cache/save@v4
         if: always()