Add ROCKROBO_S6_PURE to supported vacuums for xiaomi_miio

[OGKevin]

Breaking change

Proposed change

Upstream pr: rytilahti/python-miio#1172
The upstream PR does not need to be merged for this to work.
Temp copy paste the constant until there is a new release of the lib.

Reported: #58550 (comment)

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Additional information

• This PR fixes or closes issue: fixes Error while setting up xiaomi_miio platform for vacuum #58550
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[frenck]

So, which ones are we going to add more? Can we add them at once instead of doing multiple beta fixes? :)

[OGKevin]

I add models as folks report them and unfortunately folks have been reporting 1 by 1. I was not expecting that there would be so many supported models that have never been added to the list of supported models.
If this is becoming annoying, the code can be altered to assume all models work and don't have a mop instead.
Or this PR can remain open to collect more models.

[MartinHjelmare]

Thanks!

[MartinHjelmare]

We can think about there's a better way for next release. But for now we should just add the needed models to the list, I think.