Update cosign generate cmd to not include newline (#3393)

Removing the newline will result in a payload and sha256sum that is
equivalent to what you get with the --output-payload flag and inside
the hashedrekordobj.data.hash.value field.

Signed-off-by: Lily Sturmann <lsturman@redhat.com>

cmd/cosign/cli/generate/generate.go

@@ -49,6 +49,6 @@ func GenerateCmd(ctx context.Context, regOpts options.RegistryOptions, imageRef
 	if err != nil {
 		return err
 	}
-	fmt.Fprintln(w, string(json))
+	fmt.Fprint(w, string(json))
 	return nil
 }