arm-toolchain/gcc-arm-12.2: remove

This recipe is a rebuild from source of the Arm GCC release, with
patches from oe-core added to make it work well in our environment.

Most people are happy with the GCC in oe-core, and this release is often
behind: at the time of writing oe-core has mainline GCC 13.1, but Arm
GCC is 12.2.  Users who actually want the improvements in Arm GCC will
likely want to use the binary toolchain so that they can have support
from Arm, and they're welcome to do so via the "external-arm" binary
toolchain.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Acked-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jon Mason <jon.mason@arm.com>

ci/armgcc.yml

@@ -1,6 +0,0 @@
-header:
-  version: 11
-
-local_conf_header:
-  cc: |
-    GCCVERSION = "arm-12.2"