crypto/tls: update the MITM reference to "machine-in-the-middle"

Changing "man-in-the-middle" references to "machine-in-the-middle",
it's a more inclusive term and still aligns with the MITM acronym.

Change-Id: I81f954cff3d252433443f159ff9edaf59a28ab9d
GitHub-Last-Rev: 3e8f91424a207233b537984747ae90cbc1f03755
GitHub-Pull-Request: golang/go#37918
Reviewed-on: https://go-review.googlesource.com/c/go/+/223897
Reviewed-by: Filippo Valsorda <filippo@golang.org>
diff --git a/src/crypto/tls/common.go b/src/crypto/tls/common.go
index ef95e9b..9121148 100644
--- a/src/crypto/tls/common.go
+++ b/src/crypto/tls/common.go
@@ -549,7 +549,7 @@
 	// server's certificate chain and host name.
 	// If InsecureSkipVerify is true, TLS accepts any certificate
 	// presented by the server and any host name in that certificate.
-	// In this mode, TLS is susceptible to man-in-the-middle attacks.
+	// In this mode, TLS is susceptible to machine-in-the-middle attacks.
 	// This should be used only for testing.
 	InsecureSkipVerify bool