test: remove bug429 (duplicates runtime.TestSimpleDeadlock)

The bug429 tests is an exact duplicate of TestSimpleDeadlock in the
runtime package. The runtime package is the right place for this test,
and the version in the runtime package will run faster as the build
step is combined with other runtime package tests.

Change-Id: I6538d24e6df8e8c5e3e399d3ff37d68f3e52be56
Reviewed-on: https://go-review.googlesource.com/c/go/+/278173


Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>