net/http: remove warning when parsing a query containing a semicolon

net/http: remove warning when parsing a query containing a semicolon

It's been years since the behavior here was changed, and there's
little point in continuing to warn users of it.

Fixes #49399

Change-Id: I95f64ca14cacb64ebe78296593b1cc3d837e6b77
Reviewed-on: https://go-review.googlesource.com/c/go/+/470315
Run-TryBot: Damien Neil <dneil@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>