path: fix typo

Fixes #13419.

Change-Id: I530d0b714ea0743c72eacd07b390c3f8cc556e21
Reviewed-on: https://go-review.googlesource.com/17239Reviewed-by: Robert Griesemer <gri@golang.org>

src/path/path.go

@@ -136,7 +136,7 @@ func Clean(path string) string {
 
 // Split splits path immediately following the final slash,
 // separating it into a directory and file name component.
-// If there is no slash path, Split returns an empty dir and
+// If there is no slash in path, Split returns an empty dir and
 // file set to path.
 // The returned values have the property that path = dir+file.
 func Split(path string) (dir, file string) {