macosx: also use toggleMute for apple-script action

The previous code does not make sense as there is no unmute action.

modules/gui/macosx/CoreInteraction.m

@@ -510,15 +510,6 @@ static VLCCoreInteraction *_o_sharedInstance = nil;
     playlist_MuteToggle(pl_Get(p_intf));
 }
 
-- (void)setMute:(BOOL)b_value
-{
-    intf_thread_t *p_intf = VLCIntf;
-    if (!p_intf)
-        return;
-
-    playlist_MuteSet(pl_Get(p_intf), b_value);
-}
-
 - (BOOL)mute
 {
     intf_thread_t *p_intf = VLCIntf;

modules/gui/macosx/applescript.m

@@ -87,7 +87,7 @@
     else if ([o_command isEqualToString:@"fullscreen"])
         [[VLCCoreInteraction sharedInstance] toggleFullscreen];
     else if ([o_command isEqualToString:@"mute"])
-        [[VLCCoreInteraction sharedInstance] setMute: YES];
+        [[VLCCoreInteraction sharedInstance] toggleMute];
     else if ([o_command isEqualToString:@"volumeUp"])
         [[VLCCoreInteraction sharedInstance] volumeUp];
     else if ([o_command isEqualToString:@"volumeDown"])