Example output lacks mandatory member @timestamp.  Provide it.

Example output is not properly formatted. Fixing it by:
 - Adding '<-' to signalize it is receiving the data;
 - Adding extra spaces around members @result, @total and @completed

Signed-off-by: Victor Toso <victortoso@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
---
 qapi/dump.json | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/qapi/dump.json b/qapi/dump.json
index f7c4267e3f..9119c82b14 100644
--- a/qapi/dump.json
+++ b/qapi/dump.json
@@ -161,9 +161,10 @@
 #
 # Example:
 #
-# { "event": "DUMP_COMPLETED",
-#   "data": {"result": {"total": 1090650112, "status": "completed",
-#                       "completed": 1090650112} } }
+# <- { "event": "DUMP_COMPLETED",
+#      "data": { "result": { "total": 1090650112, "status": "completed",
+#                            "completed": 1090650112 } },
+#      "timestamp": { "seconds": 1648244171, "microseconds": 950316 } }
 #
 ##
 { 'event': 'DUMP_COMPLETED' ,
-- 
2.35.1