Remove fail: true from lychee-action config

This is now the default in v2:

https://github.com/lycheeverse/lychee-action/releases/tag/v2.0.0

.github/workflows/check_links.yml

@@ -43,5 +43,4 @@ jobs:
         uses: lycheeverse/lychee-action@7cd0af4c74a61395d455af97419279d86aafaede  # v2.0.2
         with:
           args: "--exclude-all-private --include-verbatim --max-concurrency 24 --require-https --verbose --no-progress --timeout 60 './docs/**/*.md' './docs/**/*.html' './imported_docs/**/*.md' './imported_docs/**/*.html' --exclude-path './docs/ehrql/includes/generated_docs'"
-          fail: true
           token: ${{secrets.GITHUB_TOKEN}}