removed RTD hyperlink

Author: seanpue

doc/source/index.rst

@@ -252,9 +252,8 @@ produces:
     print("hello, world!", file=sys.stderr)
 
 .. note::
-  To `adjust the CSS <https://docs.readthedocs.io/en/stable/guides/adding-custom-css.html>`_
-  of the ``stderr`` stream, use the ``stderr`` class. If you are using the default
-  Sphinx theme, for example, add the following
+  To adjust the CSS of the ``stderr`` stream, use the ``stderr`` class. If you are using
+  the default Sphinx theme, for example, add the following
   `custom CSS <https://alabaster.readthedocs.io/en/latest/customization.html#custom-stylesheet>`_:
     ``.stderr {background-color: #FCC}``.