Remove unary helpers.

isDate.js

@@ -1,5 +1,4 @@
 import baseIsDate from './_baseIsDate.js';
-import baseUnary from './_baseUnary.js';
 import nodeUtil from './_nodeUtil.js';
 
 /* Node.js helper references. */
@@ -22,6 +21,8 @@ const nodeIsDate = nodeUtil && nodeUtil.isDate;
  * _.isDate('Mon April 23 2012');
  * // => false
  */
-const isDate = nodeIsDate ? baseUnary(nodeIsDate) : baseIsDate;
+const isDate = nodeIsDate
+  ? value => nodeIsDate(value)
+  : baseIsDate;
 
 export default isDate;