more repositories for Leap 15.3

[CChalu]

Hi, `You should always have the four official repositories (which are configured out of the box).

Main Repository (OSS)
Main Repository (NON-OSS)
Main Update Repository
Main Update Repository (NON-OSS)

` I think there are more repositories in Leap 15.3 see: https://doc.opensuse.org/release-notes/x86_64/openSUSE/Leap/15.3/index.html#installation