poky: add Debian 12 to supported distribution list

The autobuilder now has a Debian 12 machine and it appears to be working
fine, so add Debian 12 to the supported list.

(From meta-yocto rev: c54fb08cc977e68295ba13942d6b3c2e82f9c86a)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-poky/conf/distro/poky.conf

@@ -41,6 +41,7 @@ SANITY_TESTED_DISTROS ?= " \
             fedora-36 \n \
             fedora-37 \n \
             debian-11 \n \
+            debian-12 \n \
             opensuseleap-15.3 \n \
             opensuseleap-15.4 \n \
             almalinux-8.7 \n \