Remove repeated parts from training notebooks 01, 02, 03, 04

[amal-ghamdi]

Description:

After adding the introductory notebook (probably the simplest BIP in the world) many concepts in CUQIpy are explained right there. We need to go through the training notebooks 01, 02, 03, 04 and remove any parts/exercises that are redundant

Definition of done:

• Parts to be removed from notebooks 01, 02, 03, 04 are determined and agreed upon (at least by two CUQIpy members)
  • Update notebook on distributions #64
• Updating the notebooks to remove the repetition is implemented, reviewed and merged