Merge pull request #108 from DoubleML/p-fix-broken-link

fix broken link to mlr3book

Author: PhilippBach

doc/guide/learners.rst

@@ -189,7 +189,7 @@ The minimum requirement for a learner to be used for nuisance models in the :ref
       To specify a specific learner in :ref:`DoubleML <doubleml_package>` users can pass objects of the class
       `Learner <https://mlr3.mlr-org.com/reference/Learner.html>`_. A fast way to construct these objects is to use the
       `mlr3 <https://mlr3.mlr-org.com/>`_  function `lrn() <https://mlr3.mlr-org.com/reference/mlr_sugar.html>`_.
-      An introduction to learners in `mlr3 <https://mlr3.mlr-org.com/>`_  is provided in the `chapter on learners of the mlr3 book <https://mlr3book.mlr-org.com/basics.html#learners>`_.
+      An introduction to learners in `mlr3 <https://mlr3.mlr-org.com/>`_  is provided in the `chapter on learners of the mlr3 book <https://mlr3book.mlr-org.com/basics.html#sec-learners>`_.
     * It is also possible to pass learners that have been constructed from a pipeline with the `mlr3pipelines <https://mlr3pipelines.mlr-org.com/>`_
       package.
     * The models `DoubleML::DoubleMLIRM <https://docs.doubleml.org/r/stable/reference/DoubleMLIRM.html>`_ and