pom: Fix url to match the actual url to the doc
This url is placed in the jar manifest as the Bundle-DocURL.
<artifactId>assertj-core</artifactId>
<version>3.23.0-SNAPSHOT</version>
+ <url>${project.parent.url}#${project.artifactId}</url>
<name>AssertJ fluent assertions</name>
<description>Rich and fluent assertions for testing for Java</description>
