fix doc [skip ci]

README.md

@@ -154,7 +154,7 @@ If these are functions, the unknown type and module name will be passed to funct
 ```lua
 function p:unknown_module(name)
   -- if can not find "foo.proto", load "my_foo.proto" instead
-  return p:load("my_"..name)
+  return p:parsefile("my_"..name)
 end
 
 function p:unknown_type(name)

README.zh.md

@@ -172,7 +172,7 @@ p.unknown_type = "Foo.*"
 ```lua
 function p:unknown_import(name)
   -- 如果找不到 "foo.proto" 文件而调用了这个函数，那就自己手动载入 "my_foo.proto" 文件并返回信息
-  return p:load("my_"..name)
+  return p:parsefile("my_"..name)
 end
 
 function p:unknown_type(name)