package/modem-manager: disable tests

tests can be disabled since version 1.20.0 and
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/commit/ba96ccc61587b7b6c31b94826ee7a3c44d795364

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/modem-manager/modem-manager.mk

@@ -14,6 +14,7 @@ MODEM_MANAGER_DEPENDENCIES = host-pkgconf dbus libglib2 $(TARGET_NLS_DEPENDENCIE
 MODEM_MANAGER_INSTALL_STAGING = YES
 MODEM_MANAGER_CONF_OPTS = \
 	-Dpowerd_suspend_resume=false \
+	-Dtests=false \
 	-Dudevdir=/usr/lib/udev
 
 ifeq ($(BR2_PACKAGE_LIBGUDEV),y)