package/sentry-native: fix double variable assignment

SENTRY_NATIVE_INSTALL_STAGING is assigned twice, causing check-package
issues:

    package/sentry-native/sentry-native.mk:13: unconditional override of
    variable SENTRY_NATIVE_INSTALL_STAGING

Fixes:
    https://gitlab.com/buildroot.org/buildroot/-/jobs/747319630

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

package/sentry-native/sentry-native.mk

@@ -6,7 +6,6 @@
 
 SENTRY_NATIVE_VERSION = 0.4.1
 SENTRY_NATIVE_SITE = $(call github,getsentry,sentry-native,$(SENTRY_NATIVE_VERSION))
-SENTRY_NATIVE_INSTALL_STAGING = YES
 SENTRY_NATIVE_LICENSE = MIT
 SENTRY_NATIVE_LICENSE_FILES = LICENSE
 SENTRY_NATIVE_DEPENDENCIES = libcurl google-breakpad