core: add /mute in default command for key alt+"=" (toggle filters)

Since v4.8.0 and commit d0298b4738, toggling
filters with `/filter toggle` displays a message on core buffer.

This is OK when running the command manually, but not when pressing the key
alt+"=".

CHANGELOG.md

@@ -6,6 +6,12 @@ SPDX-License-Identifier: GPL-3.0-or-later
 
 # WeeChat ChangeLog
 
+## Version 4.10.0 (under dev)
+
+### Changed
+
+- core: add `/mute` in default command for key `Alt`+`=` (toggle filters)
+
 ## Version 4.9.0 (2026-03-29)
 
 ### Changed

src/gui/curses/gui-curses-key.c

@@ -186,7 +186,7 @@ gui_key_default_bindings (int context, int create_option)
         BIND("meta-w,meta-b",     "/window balance");
         BIND("meta-w,meta-s",     "/window swap");
         BIND("meta-z",            "/window zoom");
-        BIND("meta-=",            "/filter toggle");
+        BIND("meta-=",            "/mute /filter toggle");
         BIND("meta--",            "/filter toggle @");
         BIND("meta-0",            "/buffer *10");
         BIND("meta-1",            "/buffer *1");