Fix documentation reference in runner docstring (#668)

* [Fix]Fix error URL in runner docstring

* [Fix]Fix error URL in runner docstring

* clean the code

mmengine/runner/runner.py

@@ -1056,14 +1056,11 @@ class Runner:
             MultiOptimWrapperConstructor which gets parameters passed to
             corresponding optimizers and compose the ``OptimWrapperDict``.
             More details about how to customize OptimizerConstructor can be
-            found at `optimizer-docs`_.
+            found at `optimizer-docs <https://mmengine.readthedocs.io/en/latest/tutorials/optim_wrapper.html>`_.
 
         Returns:
             OptimWrapper: Optimizer wrapper build from ``optimizer_cfg``.
-
-        .. _optimizer-docs:
-           https://mmengine.readthedocs.io/en/latest/tutorials/optimizer.html
-        """
+        """  # noqa: E501
         if isinstance(optim_wrapper, OptimWrapper):
             return optim_wrapper
         if isinstance(optim_wrapper, (dict, ConfigDict, Config)):