Update the documentation to reflect the change in default sts endpoint (#4576)

Author: ubaskota

docs/source/guide/configuration.rst

@@ -421,7 +421,7 @@ in the ``~/.aws/config`` file.
 ``sts_regional_endpoints``
     Sets AWS STS endpoint resolution logic. This configuration can also be set
     using the environment variable ``AWS_STS_REGIONAL_ENDPOINTS``. By default,
-    this configuration option is set to ``legacy``. Valid values are the following:
+    this configuration option is set to ``regional``. Valid values are the following:
 
     * ``regional``
         Uses the STS endpoint that corresponds to the configured Region. For
@@ -641,4 +641,4 @@ Setting it in the shared credentials or config file:
 .. code-block:: ini
 
     [default]
-    account_id_endpoint_mode=disabled
+    account_id_endpoint_mode=disabled