Merge pull request #130 from DoubleML/m-fix-mlr3book-links

fix broken link to mlr3book page

Author: MalteKurz

R/double_ml.R

@@ -719,7 +719,7 @@ DoubleML = R6Class("DoubleML",
     #' in the [mlr3tuning](https://mlr3tuning.mlr-org.com/) package. For more
     #' information on tuning in [mlr3](https://mlr3.mlr-org.com/), we refer to
     #' the section on parameter tuning in the
-    #' [mlr3 book](https://mlr3book.mlr-org.com/tuning.html).
+    #' [mlr3 book](https://mlr3book.mlr-org.com/optimization.html#tuning).
     #'
     #' @param param_set (named `list()`) \cr
     #' A named `list` with a parameter grid for each nuisance model/learner