Expected test figs in tests/figs never got updated after shortening file names

[Chris Baker]

The first time we came across the issue re: file names being too long for cran, we shortened the file names by changing the plot titles in tests/testthat/helper-funs.R (e.g., marg-plots-reflect-axis-limits-for-histograms.svg became x-axis-limits-for-histograms.svg...). This happened in
3d20d24. However, I forgot to update the expected figs in tests/figs after doing this. Tests have subsequently been skipped due to #111.