Remove legacy Web IDE frontend source code

MRs:

• Remove Legacy Web IDE frontend (!189133 - merged)
• Clean up leftover legacy Web IDE references (!189790 - merged)

Description

After removing the vscode_web_ide feature flag, clean up the legacy Web IDE implementation based on Vue 2 and Vuex.

Acceptance criteria

• Remove the unnecessary javascript modules in app/assets/javascripts/ide.
• Remove the unnecessary spec files in spec/frontend/ide
• Remove the unnecessary spec files in spec/frontend/integration/ide.
• Remove note in app/helpers/tree_helper.rb#47
• Remove a few references to the vscode_web_ide feature flag that are leftovers from Remove vscode_web_ide feature flag (!188427 - merged)
  • spec/features/ide/user_opens_merge_request_spec.rb
  • qa/qa/page/project/web_ide/vscode.rb
  • qa/qa/page/project/show.rb