Inconsistencies IHC measurement LaVision-OTOF25R

[constantinpape]

We have two numbers here: 520 and ca. 550. I think that this is because these are from two different places:

1. https://github.com/computational-cell-analytics/cochlea-net/blob/sgn-density-and-volume/scripts/figures/plot_fig6.py#L172 (the 520)
2. https://github.com/computational-cell-analytics/cochlea-net/blob/master/scripts/figures/plot_lavision.py (the ca. 550)

We should use the latter for all analysis to be more accurate.