Bug#1067620: add max version to python3-ruamel.yaml dependency

[David Mandelberg]

Hi,

Looks like python3-ruamel.yaml is at 0.18.6+ds-3 in testing and 
unstable, and whipper is failing for me now. 
https://github.com/whipper-team/whipper/issues/605#issuecomment-2073552007 
mentions a fix. Would it be possible to get that patch in Debian? (I 
haven't tested it myself though.)