qapi/trace: Tidy up trace-event-get-state, -set-state documentation

trace-event-set-state's explanation of how events are selected is
under "Features".  Doesn't belong there.  Simply delete it, as it
feels redundant with documentation of member @name.

trace-event-get-state's explanation is under "Returns".  Tolerable,
but similarly redundant.  Delete it, too.

Cc: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20230720071610.1096458-5-armbru@redhat.com>

qapi/trace.json

@@ -60,9 +60,6 @@
 #
 # Returns: a list of @TraceEventInfo for the matching events
 #
-# An event is returned if its name matches the @name pattern
-# (There are no longer any per-vCPU events).
-#
 # Since: 2.2
 #
 # Example:
@@ -90,10 +87,8 @@
 # @vcpu: The vCPU to act upon (all by default; since 2.7).
 #
 # Features:
-# @deprecated: Member @vcpu is deprecated, and always ignored.
 #
-# An event is enabled if its name matches the @name pattern
-# (There are no longer any per-vCPU events).
+# @deprecated: Member @vcpu is deprecated, and always ignored.
 #
 # Since: 2.2
 #