crypto/tls: Correct minimum version in comment

Commit 604fa4d5 made TLS 1.0 the default minimum version. This commit
amends a comment to reflect that.

This is where the default is used in the absence of an explicit version
being set:
edadffa2f3/src/crypto/tls/common.go (L391-L393)

Change-Id: I8f1117ecdddc85bb1cc76a6834026505a380b793
Reviewed-on: https://go-review.googlesource.com/5525
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>

common.go

@@ -331,7 +331,7 @@ type Config struct {
 	ClientSessionCache ClientSessionCache
 
 	// MinVersion contains the minimum SSL/TLS version that is acceptable.
-	// If zero, then SSLv3 is taken as the minimum.
+	// If zero, then TLS 1.0 is taken as the minimum.
 	MinVersion uint16
 
 	// MaxVersion contains the maximum SSL/TLS version that is acceptable.