device-generic-x86_64: fix post-install grep

grep writes to stdout and not stderr

Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/7841>

device/community/device-generic-x86_64/APKBUILD

@@ -4,7 +4,7 @@ maintainer="Clayton Craft <clayton@craftyguy.net>"
 pkgname=device-generic-x86_64
 pkgdesc="Generic x86_64 system, with EFI"
 pkgver=22
-pkgrel=1
+pkgrel=2
 url="https://postmarketos.org"
 license="MIT"
 arch="x86_64"

device/community/device-generic-x86_64/device-generic-x86_64.post-install

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 # Only display this message if none of the `oem-*` packages are installed
-if ! grep -Ex "oem-\b(\?|amd|intel)" /etc/apk/world 2>/dev/null; then
+if ! grep -Ex "oem-\b(\?|amd|intel)" /etc/apk/world >/dev/null; then
 	echo "* NOTE: This package no longer automatically installs OEM-specific drivers and firmware."
 	echo "* You will likely need to install one or both of these manually, depending on your hardware."
 	echo "* For AMD: apk add oem-amd"