ace-link-mu4e update for mu4e version >1.6

[ahttraga]

The function ace-link-mu4e checks for the variable mu4e-view-use-gnus which is obsolete as of mu4e 1.6 .

This function should be changed as follows:

;;* `ace-link-mu4e'
;;;###autoload
(defun ace-link-mu4e ()
  "Open a visible link in an `mu4e-view-mode' buffer."
  (interactive)
  (if (or (bound-and-true-p mu4e-view-use-gnus) (version<= "1.6" mu4e-mu-version))
      (ace-link-gnus)
    (let ((pt (avy-with ace-link-mu4e
                (avy-process
                 (mapcar #'cdr (ace-link--email-view-html-collect t))
                 (avy--style-fn avy-style)))))
      (ace-link--mu4e-action pt))))

where the line

(if (or (bound-and-true-p mu4e-view-use-gnus) (version<= "1.6" mu4e-mu-version))

replaces the original

(if (bound-and-true-p mu4e-view-use-gnus)