qapi/yank: Clean up documentaion of yank

The command's doc comment describes the argument, but it's not marked
up as such.  Easy enough to fix.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240205074709.3613229-11-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

qapi/pragma.json

@@ -148,8 +148,7 @@
         'query-rocker',
         'query-rocker-ports',
         'query-stats-schemas',
-        'watchdog-set-action',
-        'yank' ],
+        'watchdog-set-action' ],
     # Externally visible types whose member names may use uppercase
     'member-name-exceptions': [     # visible in:
         'ACPISlotType',             # query-acpi-ospm-status

qapi/yank.json

@@ -74,7 +74,7 @@
 # Try to recover from hanging QEMU by yanking the specified instances.
 # See @YankInstance for more information.
 #
-# Takes a list of @YankInstance as argument.
+# @instances: the instances to be yanked
 #
 # Returns:
 #     - Nothing on success