LearnerND fails for BalancingLearner test

See the pipeline https://gitlab.kwant-project.org/qt/adaptive/-/jobs/36519

added BalancingLearner Bug LearnerND labels

added Blocked label

This issue is currently blocked and !107 (merged) should be merged this.

created branch 105-learnernd-fails-for-balancinglearner-test

mentioned in merge request !112 (merged)

mentioned in issue #106 (closed)

closed via merge request !112 (merged)

mentioned in commit 73103e61