Update GranuleLocalities to be of type NotRequired[list[str]]

[gjclark]

I left the NotRequired, but I'm not sure why we're using it.

[reweeden]

NotRequired means that the field is not required, i.e. it can be left out and the UMM-G will still be valid. The JSONSchema is set up such that all of the sub-fields in SpatialExtent are optional so long as you provide any one of them. But in our type annotations we don't have the capability of doing complex validation like that so we just need to make all the fields NotRequired. As a result, an empty dict will pass type checking even though it is not valid for UMM-G, but it's the best we can do.