Fix broken Javadoc link in 0.19.0 documentation

Replace Maven variable ${project.version} with hardcoded version 0.19.0
in the Javadoc URL. The Maven-style placeholder was not being interpolated
by Jekyll, causing a broken link on the 0.19.0 documentation page.

Fixes kroxylicious/kroxylicious#3526

Assisted-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Tom Bentley <tbentley@redhat.com>

Author: tombentley

_data/documentation/0_19_0.yaml

@@ -79,5 +79,5 @@ docs:
     description: The Java API documentation.
     tags:
       - developer
-    path: "https://javadoc.io/doc/io.kroxylicious/kroxylicious-api/${project.version}/index.html"
+    path: https://javadoc.io/doc/io.kroxylicious/kroxylicious-api/0.19.0/index.html
     rank: '033'