Revert "net/url: fail TestParseErrors test when getting an unwanted error"

Revert "net/url: fail TestParseErrors test when getting an unwanted error"

This reverts https://golang.org/cl/185080.

Reason for revert: some new changes are erroring again, so this broke the builders.

Change-Id: I28da16da98b90cefbb47173d31bbbb56e43062d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/191781
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>