MDEV-36945: disable sles minor upgrade tests until after Q3 2025

[grooverdan]

Or MDEV-36945 is resolved.

The previous released packages that aren't installable onto SLES-15SP6.

note amd64-sles-1506-rpm-autobake-minor-upgrade-columnstore is unaffected, (but has a different server error about to be filed separately).

[RazvanLiviuVarzaru]

Or you can simply change the version_name to version_name: 156 in os_info.yml
and it will report that no packages were found on the mirror/archive .
See for example sles-1507 builder runs where this is already the case.

Example:
https://buildbot.mariadb.org/#/builders/962/builds/6/steps/4/logs/stdio

+ wget -q --method=HEAD https://archive.mariadb.org/mariadb-12.1/yum/sles157-amd64

This means after this release we will need:

sles156-amd64
sles157-amd64

at the mirror

[grooverdan]

works for me.

Still hoping for a portable layout so that #786 can be done and can eliminated it.
proposed MariaDB/mariadb.org-tools@576472e that will support sles156-amd64

[grooverdan]

guess no longer required.