doc: Use ROS_DOMAIN_ID 1 for the Autoware pipeline

The number of DDS participants created by the Autoware pipeline on the
Primary Compute was reaching the limit that the Safety Island memory
resources could handle. This is because DDS participants discover and
keep track of all remote endpoints, even if there is no reader/writer
match between them.

In order to limit the amount of memory used by this mechanism, isolate
the Safety Island in a dedicated Domain. This is made possible by
relying on the Message Converter component to handle the split domains.

Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>