Fix typo (clojure-emacs#491)

Author: mikepjb

clojure-mode.el

@@ -1488,7 +1488,7 @@ This function also returns nil meaning don't specify the indentation."
             ;; Preserve useful alignment of :require (and friends) in `ns' forms.
             ((and function (string-match "^:" function))
              (clojure--normal-indent last-sexp :always-align))
-            ;; This is should be identical to the :defn above.
+            ;; This should be identical to the :defn above.
             ((and function
                   (string-match "\\`\\(?:\\S +/\\)?\\(def[a-z]*\\|with-\\)"
                                 function)