fix(init): fix typo

this allows the plugin to work upon opening the first time
and will probably solve some other issues.

happy 4th of july, I'm going to buy a grill and make some wings

Fixes #40

Author: Cody Mikol

lua/neotest-kotlin/init.lua

@@ -27,7 +27,7 @@ end
 ---@param root string Root directory of project
 ---@return boolean
 function M.Adapter.filter_dir(name, rel_path, root)
-  return filter.test_directory(name)
+  return filter.is_test_directory(name)
 end
 
 ---@async