Add 'maximum.supported.desktop.version' parameter

[eibex]

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Is your feature request related to a problem? Please describe.
Prevent issues like nextcloud/desktop#4016 by allowing admins to test new versions.

Describe the solution you'd like
Add 'maximum.supported.desktop.version' config parameter, especially considering that 'minimum.supported.desktop.version' already exists

Describe alternatives you've considered
Conflicts between local and remote should result in user prompts and/or remote having more importance. This alternative should be discussed in the desktop repository though.

Additional context
n.a.

[eibex]

Relevant again with nextcloud/desktop#5564

[joshtrichards]

Should be a relatively straightforward PR (I think!) for someone with light PHP skills that is looking to get involved or contribute to Nextcloud.

Basically this, slightly modified:

https://github.com/nextcloud/server/blob/master/apps/dav/lib/Connector/Sabre/BlockLegacyClientPlugin.php

I.e. An adaptation of the existing support for minimum.supported.desktop.version that already exists.

[flooxo]

I have added a configuration parameter, but I am not sure if these tests need to be adjusted as well. Maybe you can give me some advice?
For example here:
https://github.com/nextcloud/server/blob/master/apps/dav/tests/unit/Connector/Sabre/BlockLegacyClientPluginTest.php?#L77-L81