Remove unused documents/index & documents/edit views and corresponding specs

views/documents/index is not used since `documents#index` redirects to `@project`
views/documents/edit is not used since Mercury defines its own paths and views
I certainly can, but my intention was to do nothing that was not directly related to the removal of obsolete code to keep the PR short and focused. Which ones are not so useful? e.g. `# GET /documents` before `def index`? Or `# Bryan: So that Sampriti doesn't spam us with emails`?