[Enhancement]: Disable upstream update check by default

[jayschwa]

What changes would you like?

Since updates are managed by snap, it might make sense to disable Sublime Merge's update check by default. I have it popping up right now because there's a new upstream build, but it hasn't landed in snap's stable channel yet, so there's no action for me to take. It looks like it is controlled by "update_check": false, in the Preferences.sublime-settings file. Users who wish to perform an upstream update check can still do so via the Help menu and re-enable the automatic checking.

Any extra information?

No response