Cleaning-up Extras for inconsistencies (aka golang in aarch64)

Last week I tried to build a pkg for infra, that has all the arches
enabled (so x86_64, ppc64, ppc64le and aarch64)

That package has "BuildRequires: golang >= 1.8" , which is in the base
distro but the --scratch build failed starting with aarch64 and
complaining with
"DEBUG Error: No Package found for golang >= 1.8 "

So, while there is a golang 1.8.3 package in [base], there is still an
old version in [extras] :
golang.aarch64 1.6.3-2.el7

And because koji will not pick automatically the higher ENVR, but rather
a pkg based on the repository it's coming from (with different
priorities), it doesn't want to use the one from [base], but rather the
one from [extras] (so that it impacts everybody actually building in koji)

So the proposal is : can someone have a look at cleaning-up older
releases from extras when it was replaced by a newer version that landed
in [base] ? Yum will always use the highest ENVR, but koji will not,
breaking some builds on <a href="" title=""></a> right now