ci: Exclude LinkedIn URLs from link checker

LinkedIn actively blocks automated crawlers, returning 404 for valid
profiles. Add https://www.linkedin.com/.* to the lychee exclude list
to prevent false-positive CI failures.

Signed-off-by: Dai Chen <daichen@amazon.com>

Author: dai-chen

.github/workflows/link-checker.yml

@@ -18,7 +18,7 @@ jobs:
         id: lychee
         uses: lycheeverse/lychee-action@master
         with:
-          args: --accept=200,403,429,999  "./**/*.html" "./**/*.md" "./**/*.txt" --exclude "https://aws.oss.sonatype.*|https://ci.opensearch.*|https://central.sonatype.*|http://localhost.*|https://localhost|https://odfe-node1:9200/|https://community.tableau.com/docs/DOC-17978|.*family.zzz|opensearch*|.*@amazon.com|.*email.com|.*@github.com|http://timestamp.verisign.com/scripts/timstamp.dll"
+          args: --accept=200,403,429,999  "./**/*.html" "./**/*.md" "./**/*.txt" --exclude "https://aws.oss.sonatype.*|https://ci.opensearch.*|https://central.sonatype.*|http://localhost.*|https://localhost|https://odfe-node1:9200/|https://community.tableau.com/docs/DOC-17978|.*family.zzz|opensearch*|.*@amazon.com|.*email.com|.*@github.com|http://timestamp.verisign.com/scripts/timstamp.dll|https://www.linkedin.com/.*"
         env:
           GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}
       - name: Fail if there were link errors