cmd/gomobile: remove unused binary xml
cmd/gomobile: remove unused binary xml

The removed binary XML was introduced in CL 2653 for the TestBinaryXML.
But in CL 16150, the test was reworked and the binary XML was never
used since then.

Delete it.

Change-Id: I80fd90264142bdcd4a6d88a377e36cba64088a5a
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/346389
Reviewed-by: Hajime Hoshi <1c55649263e1aefbe86bfa40d3d8351033a4d83f@gmail.com>
Run-TryBot: Hajime Hoshi <1c55649263e1aefbe86bfa40d3d8351033a4d83f@gmail.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Trust: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>

golang/mobile,golang/mobile,golang/mobile,golang/mobile