qapi/pragma: Tidy up after removal of deprecated commands

qapi/pragma: Tidy up after removal of deprecated commands

Commit cbde7be900 "migrate: remove QMP/HMP commands for speed,
downtime and cache size" neglected to remove query-migrate-cache-size
from pragma returns-whitelist.

Commit 8af54b9172 "machine: remove 'query-cpus' QMP command" neglected
to remove CpuInfo & friends from pragma name-case-exceptions.

Remove these now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20210323094025.3569441-2-armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>