[gsettings-desktop-schemas] Remove “gnome-fallback” as a valid session name.

[Carlos Garnacho <carlosg src gnome org>]

commit f0be6f8d7bc5cc240bcd390c73e43a6611b504f1
Author: Hin-Tak Leung <htl10 users sourceforge net>
Date:   Wed Jan 20 23:01:48 2021 +0000

    Remove “gnome-fallback” as a valid session name.
    
    “gnome-fallback” is no longer a valid session name for org.gnome.desktop.session/session-name. It was 
removed in 2013:
    
    commit bef001f9b0fe41ef731810e6520dcead5bd55334
    Author: Matthias Clasen <mclasen redhat com>
    Date:   Fri Jan 25 16:49:59 2013 -0500
    
        Remove the fallback session
    
        We no longer support fallback mode in 3.8, so we don't need this
        session definition anymore. We are keeping the runnable helper,
        since it sets some X properties that we need.
    
        https://bugzilla.gnome.org/show_bug.cgi?id=687586

 schemas/org.gnome.desktop.session.gschema.xml.in | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/schemas/org.gnome.desktop.session.gschema.xml.in 
b/schemas/org.gnome.desktop.session.gschema.xml.in
index 301ffa5..c999d86 100644
--- a/schemas/org.gnome.desktop.session.gschema.xml.in
+++ b/schemas/org.gnome.desktop.session.gschema.xml.in
@@ -9,8 +9,8 @@
     <key name="session-name" type="s">
       <default>"gnome"</default>
       <summary>Session type</summary>
-      <description>The name of the session to use.  Known values are
-      “gnome” and “gnome-fallback”.</description>
+      <description>The name of the session to use.  Known value is
+      “gnome”.</description>
     </key>
   </schema>
 </schemalist>