io/ioutil: don't check for short write in WriteFile

*os.File already does it.

Fixes #33064

Change-Id: I3edf0a31bf6d6e5023f47f01ebc92ed057357278
GitHub-Last-Rev: e6a5ba45d7e74def668adf145f46387ef27f5d28
GitHub-Pull-Request: golang/go#33065
Reviewed-on: https://go-review.googlesource.com/c/go/+/185857Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/io/ioutil/ioutil.go

@@ -81,10 +81,7 @@ func WriteFile(filename string, data []byte, perm os.FileMode) error {
 	if err != nil {
 		return err
 	}
-	n, err := f.Write(data)
-	if err == nil && n < len(data) {
-		err = io.ErrShortWrite
-	}
+	_, err = f.Write(data)
 	if err1 := f.Close(); err == nil {
 		err = err1
 	}