Update reference to treelite website (#7084)

treelite.io is no longer a valid site and re-directs users to a parked domain. Re-directing to the documentation is safer at this point.

doc/tutorials/model.rst

@@ -105,7 +105,7 @@ where :math:`K` is the number of trees, :math:`f` is a function in the functiona
 
 Now here comes a trick question: what is the *model* used in random forests? Tree ensembles! So random forests and boosted trees are really the same models; the
 difference arises from how we train them. This means that, if you write a predictive service for tree ensembles, you only need to write one and it should work
-for both random forests and gradient boosted trees. (See `Treelite <http://treelite.io>`_ for an actual example.) One example of why elements of supervised learning rock.
+for both random forests and gradient boosted trees. (See `Treelite <https://treelite.readthedocs.io/en/latest/index.html>`_ for an actual example.) One example of why elements of supervised learning rock.
 
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 Tree Boosting