Freeze vaadin date-picker bower dependencies in 9.10 nuxeo-web-ui build

Web UI build for 9.10 goes through without error but it produces a jar which does not contain web ui source code.

As a matter of fact, the ftest job is red:

• https://qa2.nuxeo.org/jenkins/job/9.10/job/plugins_nuxeo-web-ui-2.2_9.10/2239/

It only deploys index.jsp without any other resources (except i18n ones)

It started on March 27th 2019 revealed by https://qa2.nuxeo.org/jenkins/job/9.10/job/plugins_nuxeo-web-ui-2.2_9.10/2236/

Root cause

While backporting vaadin date-picker for 9.10 ELEMENTS-791, we did not freeze this bower dependency and they released v.3.3.3 and this commit introduced a change to rely on ../../polymer/lib/mixins/disable-upgrade-mixin.html which we don't have in our frozen other dependencies.

EDIT

9.10 >= HF28 breaks on FF < 63 because of that.