Add missing hyphen to function name

Author: samumbach

README.md

@@ -687,7 +687,7 @@ compile time constants.
  ;; bad
  (defn private-fun [] ...) ; not private at all
 
- (defn ^:private private fun [] ...) ; overly verbose
+ (defn ^:private private-fun [] ...) ; overly verbose
 
  (def private-var ...) ; not private at all
  ```