docs/system/arm/aspeed: Remove tacoma-bmc from the documentation

The tacoma-bmc machine has recently been removed, so let's remove
it from the documentation now, too.

Fixes: 2b1b66e01f ("arm: Remove tacoma-bmc machine")
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250124174507.27348-1-thuth@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
1 file changed