Update warning link to point to pyEXP API page

Author: Martin D. Weinberg

pybind11.rst

@@ -36,5 +36,5 @@ Index to pyEXP classes
       The Python API documentation can not be generated in the
       **ReadTheDocs** environment owing to memory and runtime
       limitations.  You can find these webpages that include the full
-      pyEXP API `on GitHub Pages
-      <https://exp-code.github.io/EXP-docs/>`_.
+      pyEXP API description `on GitHub Pages
+      <https://exp-code.github.io/EXP-docs/pybind11.html>`_.