test: expect "org.gnome.eog.desktop" on bullseye

After freedomofpress/securedrop-builder#349, this change is
required for SD_Viewer_Tests.test_mime_types() to pass on Debian
bullseye (thus, Qubes 4.1) and will fail on Debian buster (thus, Qubes
4.0).

tests/vars/sd-viewer.mimeapps

@@ -21,11 +21,11 @@ video/x-theora+ogg=org.gnome.Totem.desktop
 video/mp4=org.gnome.Totem.desktop
 video/x-msvideo=org.gnome.Totem.desktop
 video/x-ms-wmv=org.gnome.Totem.desktop
-image/jpeg=eog.desktop
-image/gif=eog.desktop
+image/jpeg=org.gnome.eog.desktop
+image/gif=org.gnome.eog.desktop
 image/tiff=org.gnome.Evince.desktop
-image/png=eog.desktop
-image/svg+xml=eog.desktop
+image/png=org.gnome.eog.desktop
+image/svg+xml=org.gnome.eog.desktop
 image/vnd.djvu=org.gnome.Evince.desktop
 application/vnd.rar=org.gnome.FileRoller.desktop
 application/zip=org.gnome.FileRoller.desktop