[doc] update config examples in doc/*.lua to match current syntax

doc/core.lua

@@ -69,7 +69,7 @@ end
 -- Require a specific authenticated user; put it after an auth action.
 -- Be careful: the empty username matches unauthenticated users.
 -- Example:
---   auth.plain [ "method": "basic", "realm": "test", "file": "test.plain" ];
+--   auth.plain [ "method" => "basic", "realm" => "test", "file" => "test.plain" ];
 --   auth.require_user ("foo1", "foo2");
 local function auth_require_user(...)
 	local users = {...}

doc/secdownload.lua

@@ -8,7 +8,7 @@
 --       lua.plugin "/path/secdownload.lua";
 --   }
 -- b) activate it anywhere you want:
---   secdownload [ "prefix": "/sec/", "document-root": "/secret/path", "secret": "abc", "timeout": 600 ];
+--   secdownload [ "prefix" => "/sec/", "document-root" => "/secret/path", "secret" => "abc", "timeout" => 600 ];
 
 local filename, args = ...