Deprecation of ironic-inspector was announced long ago (during 2023.2
cycle) and ironic-inspector was retired this cycle. So it's time to
drop the all remaining code to force migration to the built-in
agent interface.
Change-Id: I14a87599f9f47b167f8f1a84704982301d033381
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>