Align on org.nuxeo:nuxeo-parent release version

When releasing, org.nuxeo:nuxeo-parent must not be a SNAPSHOT version.

ATToW, the parent version on master branch is 11.4-SNAPSHOT.

1. It should be either 11.4 or 11.5-SNAPSHOT since 11.4 was released
2. if using 11.5-SNAPSHOT, then this would have to be replaced by 11.5.23 for being able to release

<parent>
  <groupId>org.nuxeo</groupId>
  <artifactId>nuxeo-ecm</artifactId>
  <version>11.5.23</version>
</parent>
<artifactId>nuxeo-parent</artifactId>
<version>11.5-SNAPSHOT</version> 

https://packages.nuxeo.com/#browse/search=keyword%3Dorg.nuxeo%3Anuxeo-parent

https://packages.nuxeo.com/repository/maven-team-platform/org/nuxeo/nuxeo-parent/11.5-SNAPSHOT/nuxeo-parent-11.5-20210105.011919-23.pom

https://packages.nuxeo.com/#browse/search=keyword%3Dorg.nuxeo%3Anuxeo-ecm%20AND%20version%3D11.5*