Court: remove code already moved to the Dev Tools package

[jaybuidl]

Follow-up on #1628

Remove DisputeTemplateView

• web/src/pages/DisputeTemplateView/
• And references to the DisputeTemplateView in apps.tsx

Remove the unused components and corresponding dependencies:

• web/src/components/JSONEditor.tsx
• Package vanilla-jsoneditor

Hidden "Dev" Menu entry

• Dev in explorer.tsx