ath79-nand: drop broken manifest alias (#3214)

fix 5deb3aae

This upgrade path never worked due to increase of the kernel partition size.
They dropped this name from SUPPORTED_DEVICES upstream:
https://github.com/openwrt/openwrt/commit/0d28e5d6440d2a37841a207f943e6e5a23172883



(cherry picked from commit 10b6d8e1198a5576e6aa8ec694c81674b7afb3fc)

Co-authored-by: Felix Baumann <felix.bau@gmx.de>

targets/ath79-nand

@@ -45,9 +45,6 @@ device('gl.inet-gl-xe300', 'glinet_gl-xe300', {
 
 device('netgear-wndr3700-v4', 'netgear_wndr3700-v4', {
 	factory_ext = '.img',
-	manifest_aliases = {
-		'netgear-wndr3700v4', -- Upgrade from OpenWrt 19.07
-	},
 })
 
 device('netgear-wndr4300', 'netgear_wndr4300', {