qapi: Fix malformed "Since:" section tags (again)

"Since X.Y" is not recognized as a tagged section, and therefore not
formatted as such in generated documentation.  Fix by adding the
required colon.

Previously fixed in commit 433a4fdc420 (qapi: Fix malformed "Since:"
section tags)

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240120095327.666239-8-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/qapi/block-core.json b/qapi/block-core.json
index ca390c5..3919156 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1361,7 +1361,7 @@
 #     target, i.e. same data and new writes are done synchronously to
 #     both.
 #
-# Since 8.2
+# Since: 8.2
 ##
 { 'struct': 'BlockJobInfoMirror',
   'data': { 'actively-synced': 'bool' } }
@@ -3080,7 +3080,7 @@
 #
 # @type: The job type
 #
-# Since 8.2
+# Since: 8.2
 ##
 { 'union': 'BlockJobChangeOptions',
   'base': { 'id': 'str', 'type': 'JobType' },