release: remove the RPI CM4s .dtb

This isn't actually packaged by the sysutils/rpi-firmware port, so we
cannot include it in the image.  Fix the RPI release build until an
interested party adds it to the port and packages are available.

Reported by:	cperciva

release/arm64/RPI.conf

@@ -4,7 +4,7 @@
 
 DTB_DIR="/usr/local/share/rpi-firmware"
 DTB="bcm2710-rpi-2-b.dtb bcm2710-rpi-3-b.dtb bcm2710-rpi-3-b-plus.dtb bcm2710-rpi-cm3.dtb \
-	bcm2711-rpi-4-b.dtb bcm2711-rpi-cm4-io.dtb bcm2711-rpi-cm4.dtb bcm2711-rpi-cm4s.dtb"
+	bcm2711-rpi-4-b.dtb bcm2711-rpi-cm4-io.dtb bcm2711-rpi-cm4.dtb"
 EMBEDDED_TARGET_ARCH="aarch64"
 EMBEDDED_TARGET="arm64"
 EMBEDDEDBUILD=1