use nilearn master to avoid issue with latest release (#6150)

Author: agramfort

.circleci/config.yml

@@ -60,6 +60,7 @@ jobs:
               pip install --user -q --upgrade pip numpy vtk
               pip install --user --progress-bar off -r requirements.txt
               pip install --user --progress-bar off ipython sphinx_fontawesome sphinx_bootstrap_theme "https://api.github.com/repos/sphinx-gallery/sphinx-gallery/zipball/master" memory_profiler "https://api.github.com/repos/nipy/PySurfer/zipball/master"
+              pip install --user --upgrade --progress-bar off "https://api.github.com/repos/nilearn/nilearn/zipball/master"
 
         - save_cache:
             key: pip-cache