sentinel-proxy: remove /etc/config folder from the package

In the version bump sentinel-proxy there was removed uci file which
should be in /etc/config. This seems like somebody forget to remove it
from the Makefile. It failed with this error:

install: cannot stat 'files/uci': No such file or directory

Fixes: d5ac0320 ("sentinel-proxy:
Release v1.3 (device token)")

collect/sentinel/sentinel-proxy/Makefile

@@ -61,9 +61,6 @@ define Package/sentinel-proxy/install
 	$(INSTALL_DIR) $(1)/etc/init.d
 	$(INSTALL_BIN) ./files/init $(1)/etc/init.d/sentinel-proxy
 
-	$(INSTALL_DIR) $(1)/etc/config
-	$(INSTALL_BIN) files/uci $(1)/etc/config/sentinel
-
 	$(INSTALL_DIR) $(1)/etc/uci-defaults
 	$(INSTALL_BIN) ./files/sentinel.uci-defaults $(1)/etc/uci-defaults/99-sentinel-main