Update colormap names to match Matplotlib's definitions

[izkgao]

This PR updates the colormap names in the preference schema to match Matplotlib's definitions.
Companion frontend PR: CARTAvis/carta-frontend#2629.

[confluence]

@izkgao The file you're modifying here is the legacy v1 preferences schema, which is no longer used and should not be modified. The current preferences schema (preferences_schema_2.json) doesn't restrict colormap fields to specific values, so no change is required.

We only use the schema to validate the field type, and rely on the frontend to manage permitted values, because our available selection is essentially arbitrary, and we shouldn't have to change the schema to add / remove colormaps. This is consistent with what we decided to do with certain numeric limits which are also arbitrary and subject to change, e.g. various data sizes.

However, I have more remarks about the frontend PR, which I will make there.