chore: remove command for viewing Clojure Grimoire

[crimeminister]

The Clojure Grimoire site (conj.io) is no longer operational. Remove the command for browsing that site.

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think a checkbox does not apply, then leave it unchecked):

• The commits are consistent with our contribution guidelines.
• You've added tests (if possible) to cover your change(s). Bugfix, indentation, and font-lock tests are extremely important!
• You've run M-x checkdoc and fixed any warnings in the code you've written.
• You've updated the changelog (if adding/changing user-visible functionality).
• You've updated the readme (if adding/changing user-visible functionality).

Thanks!

[bbatsov]

Thanks!