GitHub: migrate draft releases too

[6543]

close https://codeberg.org/Codeberg/Community/issues/447

to reproduce:

1. create draft release
2. try to migrate with releases

[codecov-commenter]

Codecov Report

Merging #15884 (a914033) into main (f582ec4) will decrease coverage by 0.09%.
The diff coverage is 54.54%.

@@            Coverage Diff             @@
##             main   #15884      +/-   ##
==========================================
- Coverage   44.01%   43.91%   -0.10%     
==========================================
  Files         681      681              
  Lines       82316    82333      +17     
==========================================
- Hits        36230    36157      -73     
- Misses      40184    40287     +103     
+ Partials     5902     5889      -13     

Impacted Files	Coverage Δ
modules/migrations/gitea_uploader.go	7.44% <0.00%> (-0.03%)	⬇️
modules/migrations/github.go	77.17% <50.00%> (-0.16%)	⬇️
modules/eventsource/manager.go	74.41% <75.00%> (+0.05%)	⬆️
modules/eventsource/manager_run.go	72.72% <78.94%> (+4.72%)	⬆️
modules/util/timer.go	42.85% <0.00%> (-42.86%)	⬇️
models/issue_comment.go	45.54% <0.00%> (-7.05%)	⬇️
modules/notification/ui/ui.go	58.97% <0.00%> (-6.84%)	⬇️
modules/notification/mail/mail.go	33.67% <0.00%> (-5.11%)	⬇️
modules/git/commit.go	52.15% <0.00%> (-4.32%)	⬇️
modules/notification/base/null.go	76.31% <0.00%> (-2.64%)	⬇️
... and 10 more

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[6543]

-> #15888