Add issues fixtures to VersionsHelperPatchTest

[ishikawa999]

Github Actionsで実行したテストが次のように失敗していました。 (https://github.com/ishikawa999/redmica_ui_extension/runs/2405924893?check_suite_focus=true)

  RAILS_ENV=test bundle exec rake test TEST=plugins/redmica_ui_extension/test
  shell: sh -e {0}
Run options: --seed 63846

# Running:

.E

Error:
VersionsHelperPatchTest#test_issues_burndown_chart_data_should_return_chart_data_without_ideal_when_due_date_earlier_than_start_date:
NoMethodError: undefined method `status=' for nil:NilClass
    plugins/redmica_ui_extension/test/helpers/versions_helper_patch_test.rb:149:in `test_issues_burndown_chart_data_should_return_chart_data_without_ideal_when_due_date_earlier_than_start_date'

bin/rails test plugins/redmica_ui_extension/test/helpers/versions_helper_patch_test.rb:143

.E

Error:
VersionsHelperPatchTest#test_issues_burndown_chart_data_should_return_chart_data_without_ideal:
NoMethodError: undefined method `[]' for nil:NilClass
    plugins/redmica_ui_extension/test/helpers/versions_helper_patch_test.rb:128:in `test_issues_burndown_chart_data_should_return_chart_data_without_ideal'

bin/rails test plugins/redmica_ui_extension/test/helpers/versions_helper_patch_test.rb:122

...Capybara starting Puma...
* Version 5.2.2 , codename: Fettisdagsbulle
* Min threads: 0, max threads: 4
* Listening on http://172.18.0.2:3000
........

Finished in 22.672664s, 0.6616 runs/s, 2.0730 assertions/s.
15 runs, 47 assertions, 0 failures, 2 errors, 0 skips

VersionsHelperPatchTestでfixtures: :issuesが読み込まれていないことで、version.fixed_issues.lastがnilになっているようです。 fixtures: :issuesを追加したので、念のため確認をお願いいたします。(ご確認いただけましたら私がマージします。)

https://github.com/ishikawa999/redmica_ui_extension/actions/runs/772643347 (これと同様の変更を行った後のテストがすべて成功している様子)

[ishikawa999]

マージしました