qapi: Fix misspelled references

qapi: Fix misspelled references

query-cpu-definitions returns a list of CpuDefinitionInfo, but
documentation claims CpuDefInfo, which doesn't exist.

query-migrate-capabilities returns a list of
MigrationCapabilityStatus, but documentation claims
MigrationCapabilitiesStatus, which doesn't exist.

balloon and query-balloon can fail with KVMMissingCap, but
documentation claims KvmMissingCap, which doesn't exist.

Fix the documentation.

Fixes: e4e31c6324af (qapi: add query-cpu-definitions command (v2))
Fixes: bbf6da32b5bd (Add migration capabilities)
Fixes: d72f326431e2 (qapi: Convert balloon)
Fixes: 96637bcdf9e0 (qapi: Convert query-balloon)
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <20230425064223.820979-4-armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>