http2: fix up comment on unexported connError type
http2: fix up comment on unexported connError type

It apparently used to be called connErrorReason but when it was
renamed the comment wasn't updated. Also, the comment was split via a
blank line, detaching it from its decl node.

Change-Id: I4ae510fc0e48fd61f40489428f9da4c6cab3ef2f
Reviewed-on: https://go-review.googlesource.com/45273
Reviewed-by: Hiroshi Ioka <df78038fc5538a7e68ba2383ae82f13c817a6cd1@gmail.com>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/net