net/http: drop mimesniff for audio/basic
net/http: drop mimesniff for audio/basic

The WHATWG Mime Sniffing Standard we follow dropped support for
.snd / audio/basic.
https://github.com/whatwg/mimesniff/issues/151

Change-Id: Iae1bd8b29063b06b5b3909a944e12ead5974a526
Reviewed-on: https://go-review.googlesource.com/c/go/+/400754
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
Auto-Submit: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Auto-Submit: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Reviewed-by: Damien Neil <7e091e9a80da888fcd7836fd3c6b7b85f4677c12@google.com>

nawawi/go,golang/go,golang/go,nawawi/go,golang/go,golang/go,nawawi/go,golang/go,golang/go,golang/go,nawawi/go,nawawi/go,nawawi/go,golang/go,nawawi/go,nawawi/go