tests/netstats_l2: build only for boards providing netif feature

The BOARD_PROVIDES_NETIF variable is now useless and can be removed

tests/netstats_l2/Makefile

@@ -1,12 +1,7 @@
 include ../Makefile.tests_common
 
-BOARD_PROVIDES_NETIF := airfy-beacon fox iotlab-m3 mulle native nrf51dk nrf51dongle \
-	nrf6310 pba-d-01-kw2x samd21-xpro saml21-xpro samr21-xpro spark-core \
-	yunjia-nrf51822 \
-    esp32-mh-et-live-minikit esp32-olimex-evb \
-    esp32-wemos-lolin-d32-pro esp32-wroom-32 esp32-wrover-kit
-
-BOARD_WHITELIST += $(BOARD_PROVIDES_NETIF)
+# This application runs by default on boards providing the netif feature
+FEATURES_REQUIRED += netif
 
 USEMODULE += shell
 USEMODULE += shell_commands