Build using Maven latest version (3.9.4)

• Update Maven to latest version in GitLab CI configuration file.
• Moving from 3.8.4 to 3.9.4 lead to an update of maven-antrun-plugin as version is not specified in pom.xml nor in OW2 parent pom.xml (update is triggered by version defined in Maven super pom see: https://maven.apache.org/ref/3.9.4/maven-model-builder/super-pom.html). Changes introduce in maven-antrun-plugin version 3.0.0 (see https://maven.apache.org/plugins/maven-antrun-plugin/) requires some changes in the plugin configuration: parameter tasks is replaced by target. This commit include required updates.