When TRANSLATION_BRANCH is undefined, we're not building a website which
needs translations. However because of the way many website projects
lego packages, by symlinking
such builds are always created with the
i18n plugin present.
This is not harmless: at present, if a python >=3.9 build environment is used, this plugin will corrupt all builds with PO-file garbage.
By removing the plugin prior to a deployment build, we work around this problem, while at the same time likely improve build times.