Remove web ui mp version from nuxeo-distribution

We currently have nuxeo-distribution/pom.xml referencing the web ui mp version that some other addon marketplace like nuxeo-dam can run their functional tests. (see https://github.com/nuxeo/marketplace-dam/blob/master/ftest/web-ui/webdriver/itests.xml#L13).

We should not do that and rather evolve the https://github.com/nuxeo/integration-scripts/blob/master/marketplace.ini to proceed to version replacement when releasing the mp.