Fix docstring.

packages/markitdown/src/markitdown/_markitdown.py

@@ -111,6 +111,7 @@ class MarkItDown:
         """
         Enable and register built-in converters.
         Built-in converters are enabled by default.
+        This method should only be called once, if built-ins were initially disabled.
         """
         if not self._builtins_enabled:
             # TODO: Move these into converter constructors

packages/markitdown/src/markitdown/converters/_base.py

@@ -37,7 +37,6 @@ class DocumentConverter:
         We have tight control over the order of built-in converters, but
         plugins can register converters in any order. A converter's priority
         field reasserts some control over the order of converters.
-        This method should only be called once, if built-ins were initially disabled.
 
         Plugins can register converters with any priority, to appear before or
         after the built-ins. For example, a plugin with priority 9 will run