qapi: Inline and remove QERR_MIGRATION_ACTIVE definition

Address the comment added in commit 4629ed1e98
("qerror: Finally unused, clean up"), from 2015:

  /*
   * These macros will go away, please don't use
   * in new code, and do not add new ones!
   */

Mechanical transformation using sed, manually
removing the definition in include/qapi/qmp/qerror.h.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240312141343.3168265-10-armbru@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
[Straightforward conflict with commit aeaafb1e59f (migration: export
migration_is_running) resolved]
4 files changed