qapi: fix example of query-dump-guest-memory-capability command

Example output is missing closing curly brackets. Fix it.

Problem was noticed when trying to load the example into python's json
library.

Signed-off-by: Victor Toso <victortoso@redhat.com>
Message-Id: <20220901085840.22520-4-victortoso@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

qapi/dump.json

@@ -195,7 +195,7 @@
 #
 # -> { "execute": "query-dump-guest-memory-capability" }
 # <- { "return": { "formats":
-#                  ["elf", "kdump-zlib", "kdump-lzo", "kdump-snappy"] }
+#                  ["elf", "kdump-zlib", "kdump-lzo", "kdump-snappy"] } }
 #
 ##
 { 'command': 'query-dump-guest-memory-capability',