[gimp] desktop: add (bogus) date for 2.99.12 release.

[Jehan <jehanp src gnome org>]

commit 6895631388192f567a4c3eb1c3dafc82d07ef718
Author: Jehan <jehan girinstud io>
Date:   Tue May 3 23:43:32 2022 +0200

    desktop: add (bogus) date for 2.99.12 release.
    
    appstreamcli on CI fails with error:
    
    > E: org.gimp.GIMP:394: release-time-missing date
    
    I didn't have such error on my local build, because it is a new check
    only recently added. The CI appstreamcli errored-out this way.
    
    It forces us to add a bogus release date since we don't know it yet. I
    chose May 29, because we usually release on Sundays, and it might soon
    be time to make a dev release (so who knows, we might get lucky and it
    might happen this day), though it should not be taken as a promise or a
    real plan just now. I just needed to fill something in, in order to fix
    the CI.
    
    I opened a report to ask that appstreamcli proposes a relaxed check mode
    where we can test on the <release> tag before knowing the future date:
    https://github.com/ximion/appstream/issues/398

 desktop/org.gimp.GIMP.appdata.xml.in.in | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/desktop/org.gimp.GIMP.appdata.xml.in.in b/desktop/org.gimp.GIMP.appdata.xml.in.in
index f9ecd5b292..6f556c6a7a 100644
--- a/desktop/org.gimp.GIMP.appdata.xml.in.in
+++ b/desktop/org.gimp.GIMP.appdata.xml.in.in
@@ -74,7 +74,7 @@
   </provides>
 
   <releases>
-    <release version="2.99.11" type="development">
+    <release version="2.99.12" date="2022-05-29" type="development">
       <description>
         <_p>
         One step further towards GIMP 3.0, GIMP 2.99.12 comes along with the following noteworthy 
improvements: