bug: sic_classification doesn't seem to be consistent with current SIC codes online

[jdhoffa]

The codes in the exported sic_classification dataset require 5-digit codes:

The SIC code database only allows codes containing a maximum of 4-digits:

It is very likely that the sic_classification dataset is outdated, as it was first merged 4 years ago.

Possible actions (not mutually exclusive):
Determine if the dataset is referring to some different SIC classification system
Deprecate the sic_classification dataset
Update the sic_classification dataset to the latest version

AB#10292

[jdhoffa]

It seems that this system is consistent with the south African SIC codes:
https://www.statssa.gov.za/additional_services/sic/mdvdvmg4.htm#MAJOR%20DIVISIONS,DIVISIONS%20AND%20MAJOR%20GROUPS