Update lychee

Author: adamlaki

.github/workflows/test.yml

@@ -78,13 +78,13 @@ jobs:
             uses: actions/checkout@v4
         -
             name: Run Lychee
-            uses: lycheeverse/lychee-action@v1
+            uses: lycheeverse/lychee-action@v2
             with:
                 args: >-
                     --verbose
                     --no-progress
                     --require-https
-                    --max-concurrency 2
+                    --max-concurrency 4
                     --user-agent 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36'
                     './**/*.md'
                 output: ${{ runner.temp }}/lychee/out.md