net/http/cgi: remove port from the CGI environment of variable SERVER_NAME
The SERVER_NAME variable in the CGI environment should not
contain the port, according to the section 4.1.14 of the
RFC 3875.
Fixes #53368.
Change-Id: Ifeea70206878cf83bc0bda35cb514d0226bbcd8c
Reviewed-on: https://go-review.googlesource.com/c/go/+/412434
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Damien Neil <dneil@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: xie cui <523516579@qq.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>