Remove duplicated "by which" words from the doc (#3534)

AlexanderLukin · jdalton · commit b2ea6b1cd251 · 2017-12-06T00:06:26.000-08:00
diff --git a/xorBy.js b/xorBy.js
@@ -6,7 +6,7 @@ import last from './last.js'
 /**
  * This method is like `xor` except that it accepts `iteratee` which is
  * invoked for each element of each `arrays` to generate the criterion by
- * which by which they're compared. The order of result values is determined
+ * which they're compared. The order of result values is determined
  * by the order they occur in the arrays. The iteratee is invoked with one
  * argument: (value).
  *

Original file line number	Diff line number	Diff line change
`@@ -6,7 +6,7 @@ import last from './last.js'`
`6`	`6`	`/**`
`7`	`7`	* This method is like `xor` except that it accepts `iteratee` which is
`8`	`8`	* invoked for each element of each `arrays` to generate the criterion by
`9`		`- * which by which they're compared. The order of result values is determined`
	`9`	`+ * which they're compared. The order of result values is determined`
`10`	`10`	`* by the order they occur in the arrays. The iteratee is invoked with one`
`11`	`11`	`* argument: (value).`
`12`	`12`	`*`