Sync clojure-mode-extra-font-locking.el version with clojure-mode.el

[manphiz]

• It looks like the version of clojure-mode-extra-font-locking.el has been out-of-sync with clojure-mode.el and has been stuck in 3.0.0 for a long time.
• This patch sync the version with the current snapshot.

Note: it would be great to fix 5.18.x branch but not really needed I guess.

• [X] The commits are consistent with our [contribution guidelines][1].
• [ ] You've added tests (if possible) to cover your change(s). Bugfix, indentation, and font-lock tests are extremely important!
• [X] You've run M-x checkdoc and fixed any warnings in the code you've written.
• [X] You've updated the changelog (if adding/changing user-visible functionality).
• [ ] You've updated the readme (if adding/changing user-visible functionality).