qapi/machine.json: Fix missing newline in doc comment

In commit 176d2cd we added the @die-id field
to the CpuInstanceProperties struct, but in the process
accidentally removed the newline between the doc-comment
lines for @core-id and @thread-id.

Put the newline back in; this fixes a misformatting in the
generated HTML QMP reference manual.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20200729191019.19168-1-peter.maydell@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

qapi/machine.json

@@ -825,7 +825,8 @@
 # @node-id: NUMA node ID the CPU belongs to
 # @socket-id: socket number within node/board the CPU belongs to
 # @die-id: die number within node/board the CPU belongs to (Since 4.1)
-# @core-id: core number within die the CPU belongs to# @thread-id: thread number within core the CPU belongs to
+# @core-id: core number within die the CPU belongs to
+# @thread-id: thread number within core the CPU belongs to
 #
 # Note: currently there are 5 properties that could be present
 #       but management should be prepared to pass through other