[std] fix documentation of StringTools.replace

closes #7480

std/StringTools.hx

@@ -384,9 +384,8 @@ class StringTools {
 		String `by`.
 
 		If `sub` is the empty String `""`, `by` is inserted after each character
-		of `s`. If `by` is also the empty String `""`, `s` remains unchanged.
-
-		This is a convenience function for `s.split(sub).join(by)`.
+		of `s` except the last one. If `by` is also the empty String `""`, `s`
+		remains unchanged.
 
 		If `sub` or `by` are null, the result is unspecified.
 	**/