package/trace-cmd: installs nothing in staging/

Since its introduction in Buildroot in 2013 with commit 07203d78c24d
(trace-cmd: new package), trace-cmd has declared installing in staging.

But trace-cmd is a generic-package, and has never, ever provided any
commands for staging installation.

Drop this declaration.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/trace-cmd/trace-cmd.mk

@@ -7,7 +7,6 @@
 TRACE_CMD_VERSION = trace-cmd-v2.9.1
 TRACE_CMD_SITE = https://git.kernel.org/pub/scm/utils/trace-cmd/trace-cmd.git
 TRACE_CMD_SITE_METHOD = git
-TRACE_CMD_INSTALL_STAGING = YES
 TRACE_CMD_LICENSE = GPL-2.0, LGPL-2.1
 TRACE_CMD_LICENSE_FILES = COPYING COPYING.LIB LICENSES/GPL-2.0 LICENSES/LGPL-2.1