Migrate some specs to Jest

What does this MR do?

Migrate some specs to Jest

• [ee] boards/components/board_list_selector/board_list_selector_spec.js
• [ee] issuable/related_issues/stores/related_issues_store_spec.js
• boards/board_list_helper.js (this was a helper, so renamed to reflect that)
• Removed helpers/vuex_action_helper_spec.js - already exists in Jest

References

• #194291 (closed)
• #194272 (closed)