Prefer https submodules (#2397)

Author: gepbird

.gitmodules

@@ -57,7 +57,7 @@
 	url = https://github.com/LuaCATS/skynet.git
 [submodule "meta/3rd/ffi-reflect"]
 	path = meta/3rd/ffi-reflect
-	url = git@github.com:LuaCATS/ffi-reflect.git
+  url = https://github.com/LuaCATS/ffi-reflect.git
 [submodule "meta/3rd/luv"]
 	path = meta/3rd/luv
-	url = git@github.com:LuaCATS/luv.git
+  url = https://github.com/LuaCATS/luv.git