fix diagram display of transition parameters

[avallecam]

@avallecam: could you please slightly reduce the size of the figure so that all the labels and the text on the arrows are fully visible? At the moment, the text from v₁ to v₂ is only partially displayed.

Originally posted by @Degoot-AM in #94 (comment)

[avallecam]

solved locally but not online. section https://epiverse-trace.github.io/tutorials-late/compare-interventions.html#vacamole-model