Fix fail condition in link checker

[mre]

Fix fail condition for lychee link checker:
The link checker is currently misconfigured and fails with an error message:

Run lycheeverse/[email protected]
Run curl -sLO "https://github.com/lycheeverse/lychee/releases/download/v0.13.0/lychee-v0.13.0-x86_64-unknown-linux-gnu.tar.gz"
lychee
Run /home/runner/work/_actions/lycheeverse/lychee-action/v1.8.0/entrypoint.sh
error: unexpected argument '--fail' found

  note: to pass '--fail' as a value, use '-- --fail'

Usage: lychee --format <FORMAT> --output <OUTPUT> --no-progress <--verbose...|--quiet...> <inputs>...

For more information, try '--help'.

The reason is that the syntax is incorrect. --fail is not a flag of lychee, but a parameter of lychee-action.

Description:

• Fixes the syntax and passes fail: true to the action.
• Removes the non-existent --fail flag

Motivation:
The misconfigured action silently ignored link checking issues.
As a consequence, some links are currently broken, but that's a separate issue.