transmission-web: set conflicts with transmission-web-control

Signed-off-by: Richard Yu <yurichard3839@gmail.com>

net/transmission/Makefile

@@ -86,6 +86,7 @@ define Package/transmission-web
   $(call Package/transmission/template)
   TITLE+= (webinterface)
   DEPENDS:=@(PACKAGE_transmission-daemon-openssl||PACKAGE_transmission-daemon-mbedtls)
+  CONFLICTS:=transmission-web-control
   PKGARCH:=all
 endef