Revert "net/http/cgi: workaround for closure inlining issue"

Revert "net/http/cgi: workaround for closure inlining issue"

This reverts CL 522935.

Issue #62277 is fixed, the workaround can be dropped.

Updates #62277

Change-Id: I7c69e35248942b4d4fcdd81121051cca9b098980
Reviewed-on: https://go-review.googlesource.com/c/go/+/523175
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>