Remove "s" flag for MIGRATE in command table.

Maybe there are legitimate use cases for MIGRATE inside Lua scripts, at
least for now. When the command will be executed in an asynchronous
fashion (planned) it is possible we'll no longer be able to permit it
from within Lua scripts.

src/server.c

@@ -265,7 +265,7 @@ struct redisCommand redisCommandTable[] = {
     {"cluster",clusterCommand,-2,"ar",0,NULL,0,0,0,0,0},
     {"restore",restoreCommand,-4,"wm",0,NULL,1,1,1,0,0},
     {"restore-asking",restoreCommand,-4,"wmk",0,NULL,1,1,1,0,0},
-    {"migrate",migrateCommand,-6,"ws",0,NULL,3,3,1,0,0},
+    {"migrate",migrateCommand,-6,"w",0,NULL,3,3,1,0,0},
     {"asking",askingCommand,1,"r",0,NULL,0,0,0,0,0},
     {"readonly",readonlyCommand,1,"rF",0,NULL,0,0,0,0,0},
     {"readwrite",readwriteCommand,1,"rF",0,NULL,0,0,0,0,0},