undo CL 64820044 / 4f9dee8402af

Callers of md5.Sum should do so to avoid allocations, the example did not demonstate this property.

««« original CL description
crypto/md5: add example for Sum

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/64820044

»»»

LGTM=minux.ma
R=r, minux.ma
CC=golang-codereviews
https://golang.org/cl/65180043

src/pkg/crypto/md5/example_test.go

@@ -17,9 +17,3 @@ func ExampleNew() {
 	fmt.Printf("%x", h.Sum(nil))
 	// Output: e2c569be17396eca2a2e3c11578123ed
 }
-
-func ExampleSum() {
-	input := "The quick brown fox jumps over the lazy dog."
-	fmt.Printf("%x", md5.Sum([]byte(input)))
-	// Output: e4d909c290d0fb1ca068ffaddf22cbd0
-}