release: adjust lang/python* dependencies for GCE

The lang/python3 port had failed to properly install because
it did in fact already exist and FORCE_PKG_REGISTER was not
set. So, behaviorally everything here was correct. However,
installing lang/python3 is in fact not correct and not needed,
so only install the lang/python port to provide symbolic links.

PR: 272354
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(cherry picked from commit b24c35b326dbd355070335e63d02e7c29ee58bf0)