Remove deprecated codes (#5812)

Author: huangdijia

src/Container.php

@@ -146,14 +146,6 @@ public function has($id): bool
         return true;
     }
 
-    /**
-     * @deprecated
-     */
-    public function getDefinitionSource(): Definition\DefinitionSourceInterface
-    {
-        return $this->definitionSource;
-    }
-
     /**
      * @param array|callable|string $definition
      */