build/release: remove ARM based darwin from release scripts

These result in an error with the current release script as is. Those
that want to run `lnd` on their iPhone/iPad can instead use the
`gomobile` bindings.

build/release/release.sh

@@ -40,8 +40,6 @@ cd $MAINDIR
 SYS=${LNDBUILDSYS:-"
         darwin-386
         darwin-amd64
-        darwin-arm
-        darwin-arm64
         dragonfly-amd64
         freebsd-386
         freebsd-amd64