coreboot-sdk/Dockerfile: Remove explicit install of 'm4'

Remove m4 as an explicity installed package as it will be
installed automatically by flex and bison.

Change-Id: Ic4f1c5e6f3324429914bf593047d802dfcc0cb30
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/82512
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/docker/coreboot-sdk/Dockerfile

@@ -61,7 +61,6 @@ RUN \
 		libusb-1.0-0-dev \
 		libxml2-dev \
 		libyaml-dev \
-		m4 \
 		make \
 		meson \
 		msitools \