Temporarily disable Save to Cloud option for Beta release

[cbjeukendrup]

Resolves: https://trello.com/c/TiatpJIG/57-disable-save-to-cloud-option-for-beta-release

We need to prevent users trying to upload scores, since the version on MuseScore.com will still be using 3.5.2.
It doesn't make sense to update the MuseScore.com version until we are satisfied that 3.6 is stable.

(I hope this is the desired way to do this. Obviously it should be reverted again, at some point.)

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• I created the test (mtest, vtest, script test) to verify the changes I made

[Jojo-Schmitz]

Maybe allowing for this in experimental mode? So we can test whether Save Online works at all?

[cbjeukendrup]

@Jojo-Schmitz You should actually ask @vpereverzev, but I thought the point was that things could go wrong on musescore.com if 'too new' files would be uploaded.

[vpereverzev]

We just can't upload anything since backend of musescore.com uses older version than ours. That's why we shouldn't confuse people.

[Jojo-Schmitz]

If it were hidden behind the -x (experimental) option, there would be no confusion, but those knowing this could test, lika (also) the translations

[vpereverzev]

no matter of unstable or experimental mode, you'll get problems with "upload score" feature, because of the backend of musescore.com

there is nothing to test here, it won't process your score anyway

[Jojo-Schmitz]

You get that only after the attempts, after having seen the dialog(s) and its translation. No harm on the server, just a test drill