Update plugin artifactId to soapui-extension-maven-plugin

[redfish4ktc]

The current artifactId does not follow maven convention

[ERROR]`Artifact Ids of the format maven-___-plugin are reserved for
plugins in the Group Id org.apache.maven.plugins
Please change your artifactId to the format ___-maven-plugin
In the future this error will break the build.

The update could be done when

• the following soapui pull request has been merged or implemented in another way
• the new release of the plugin integrates the change

Be carreful, we need to document this change in the README/wiki. Expecially, document starting which version the modification applies.

[redfish4ktc]

Starting from soapui 4.5.2, SmartBear maven plugin artifactId are soapui-maven-plugin and soapui-pro-maven-plugin Stable release are available with these artifactId starting from 4.6.1