Change active_by_default server default from False to True

[soininen]

New databases now come with active_by_default column default set to True. A migration script handles updates of old databases. There was no need to modify the compatibility functions as discussed in the issue: we already set active_by_default unconditionally to True.

Resolves spine-tools/Spine-Toolbox#2744

Checklist before merging

• [x] Documentation (also in Toolbox repo) is up-to-date
• [x] Release notes in Toolbox repo have been updated
• [x] Unit tests have been added/updated accordingly
• [x] Code has been formatted by black
• [x] Unit tests pass

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 91.66667% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 78.29%. Comparing base (558c32c) to head (c627fc0).

Files	Patch %	Lines
...7927a5_change_active_by_default_server_default_.py	90.90%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #399 +/- ## ======================================= Coverage 78.29% 78.29% ======================================= Files 75 76 +1 Lines 9503 9514 +11 Branches 2011 2012 +1 ======================================= + Hits 7440 7449 +9 - Misses 1733 1734 +1 - Partials 330 331 +1 ```

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