Add valid_till to OpenMandriva 4.x

[dreua]

According to Wikipedia all the 4.x versions are unmaintained. I couldn't find any official eol information though, but in their support forums questions regarding those versions are also tagged eol.

repology-updater/repos.d/rpm/openmandriva.yaml

Lines 68 to 70 in 2a4977a

	{{ openmandriva("4.1", archived=True, minpackages=10000) }}
	{{ openmandriva("4.2", archived=True, minpackages=11000) }}
	{{ openmandriva("4.3", minpackages=11000) }}

I think a valid_till has to added here but I haven't looked into the makros in depth, maybe those need to changed as well to support it?

[dreua]

Same thing for Devuan 3: https://en.wikipedia.org/wiki/Talk:Devuan

Let me know in case you want separete issus for that.