Fix doc by using relative link to apache camel website

[apupier]

introduced by
aa22a61 the doc PR validation has not caught it
https://github.com/apache/camel/actions/runs/26436265031/job/77819715735

the error was:

/home/jenkins/712657a4/workspace/Camel_Camel.website_main/camel-website/public/manual/camel-jbang-mcp.html

[check:html     ]   41:5221  error  For links within camel.apache.org
use relative links, found:
https://camel.apache.org/manual/camel-jbang.html

Description

Target

• I checked that the commit is targeting the correct branch (Camel 4 uses the main branch)

Tracking

• If this is a large change, bug fix, or code improvement, I checked there is a JIRA issue filed for the change (usually before you start working on it).

Apache Camel coding standards and style

• I checked that each commit in the pull request has a meaningful subject line and body.

• I have run mvn clean install -DskipTests locally from root folder and I have committed all auto-generated changes.

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

• docs

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