spotRiver v0.2.10 released

Starting with River 0.21.0, River’s learn_one and learn_many methods of each estimator don’t not return anything anymore, see https://riverml.xyz/0.21.0/releases/0.21.0/. This is to emphasize that the estimators are stateful. spotRiver >= 0.2.10 reflects these changes. spotRiver is available on https://github.com/sequential-parameter-optimization/spotRiver