Don't call Cmd_RemoveCommand for nonexistent commands

Some of them do exist, but are now implemented with new-style commands
so the legacy interface shouldn't be used.

src/engine/client/cl_main.cpp

@@ -2474,18 +2474,15 @@ void CL_Shutdown()
 
 	Cmd_RemoveCommand( "cmd" );
 	Cmd_RemoveCommand( "configstrings" );
-	Cmd_RemoveCommand( "userinfo" );
 	Cmd_RemoveCommand( "snd_restart" );
 	Cmd_RemoveCommand( "vid_restart" );
 	Cmd_RemoveCommand( "disconnect" );
 	Cmd_RemoveCommand( "connect" );
 	Cmd_RemoveCommand( "localservers" );
 	Cmd_RemoveCommand( "globalservers" );
-	Cmd_RemoveCommand( "rcon" );
 	Cmd_RemoveCommand( "ping" );
 	Cmd_RemoveCommand( "serverstatus" );
 	Cmd_RemoveCommand( "showip" );
-	Cmd_RemoveCommand( "model" );
 
 	CL_ClearKeyBinding();
 	CL_ClearInput();

src/engine/renderer/tr_init.cpp

@@ -1535,8 +1535,6 @@ ScreenshotCmd screenshotPNGRegistration("screenshotPNG", ssFormat_t::SSF_PNG, "p
 
 		ri.Cmd_RemoveCommand( "shaderexp" );
 		ri.Cmd_RemoveCommand( "gfxinfo" );
-		ri.Cmd_RemoveCommand( "shaderstate" );
-		ri.Cmd_RemoveCommand( "generatemtr" );
 		ri.Cmd_RemoveCommand( "buildcubemaps" );
 
 		ri.Cmd_RemoveCommand( "glsl_restart" );

src/engine/server/sv_ccmds.cpp

@@ -451,6 +451,5 @@ void SV_RemoveOperatorCommands()
 	Cmd_RemoveCommand( "heartbeat" );
 	Cmd_RemoveCommand( "map_restart" );
 	Cmd_RemoveCommand( "serverinfo" );
-	Cmd_RemoveCommand( "status" );
 	Cmd_RemoveCommand( "systeminfo" );
 }