simplify renku dataset notebook with climetlab=0.7

• loop over dates not needed any more

added improvement label

tackle together with https://renkulab.io/gitlab/aaron.spring/s2s-ai-challenge-template/-/issues/3

mentioned in merge request !14 (merged)

mentioned in merge request tasko.olevski/s2s-ai-competition-scoring-image!3 (merged)

closed with merge request !14 (merged)

mentioned in commit 48fd739a

mentioned in commit tasko.olevski/s2s-ai-competition-scoring-image@0dc85cbe