device/google-sargo: Move from testing to community

It is surprisingly well supported and will likely be the first Android device with both cameras working. With sufficient maintainership we might even be able to promote it to main.

Should land together with https://gitlab.com/postmarketOS/postmarketos.org/-/merge_requests/290

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See also:

• https://gitlab.com/postmarketOS/build.postmarketos.org/-/merge_requests/110
• !5453 (merged)

cc @flamingradian