Check micromole handling in Harmonize_CapeCod_Detailed.ipynb

In the notebook: Harmonize_CapeCod_Detailed.ipynb
When running:
```Python
# Organic carbon (%)
df = harmonize.harmonize(df, 'Organic carbon', report=True)
```
Error:
```Python
DimensionalityError: Cannot convert from 'micromole * water / liter' ([substance] * [mass] / [length] ** 6) to 'milligram / liter' ([mass] / [length] ** 3)
```
