More conversions of $.ajax to axios

What does this MR do?

Converts the following to axios:

• app/assets/javascripts/project_label_subscription.js
• app/assets/javascripts/prometheus_metrics/prometheus_metrics.js
• app/assets/javascripts/protected_branches/protected_branch_edit.js
• app/assets/javascripts/protected_tags/protected_tag_edit.js
• app/assets/javascripts/right_sidebar.js
• app/assets/javascripts/shortcuts.js
• app/assets/javascripts/task_list.js

What are the relevant issue numbers?

#42397 (closed)