refactor(GUI): enlarge the left and right margins of the exported Model Diagram

Refs #54
2 jobs for 54-resize-model-diagram-plot-exported-from-teh-gui in 5 minutes and 58 seconds (queued for 8 seconds)
Status Name Job ID Coverage
  Check
passed check_devel_airGR_cran #238894
docker

00:05:17

passed check_devel_airGR_notcran #238895
docker

00:05:58