Post-analysis visualization graph layout

(Originally reported by @dorothyparry3)

[In the post-analysis episode 32-analysis-tuning.md, currently there is this plot to show the effect of tuning of num of hidden neurons]:

I'm just wondering if we should change the format of the visualization. Are we sure we like the format with the 4 different subplots? Or did we want to combine the validation and the training into one plot (each)?