Comment # 4 on bug 1171018 from Neil Rickert

I normally use the DVD installer.

After installation, I see the same repos, with one exception.  The one that you
list second ("openSUSE-Leap-15.1-1") is accessing the repo that is onboard the
installer DVD itself.  And, after the install has completed, that repo is
disabled.

I have not recently tried using the NET installer.  If it also disables that
repo, then the redundancy should not actually matter.  And you should be able
to delete that repo, with no harm done.  It is needed for the install, because
some of the installer software may be downloaded from there during the
installation.