use also dev of mlr3learners in mlr3dev workflows, see mlr-org/mlr3learners#325

Author: PhilippBach

.github/workflows/rcheck.yml

@@ -80,6 +80,7 @@ jobs:
         run: |
           remotes::install_github("mlr-org/mlr3")
           remotes::install_github("mlr-org/paradox")
+          remotes::install_github("mlr-org/mlr3learners")
         shell: Rscript {0}
 
       - name: Check