Update delphi_utils.geomapper to 2020 FIPS population data

[dshemetov]

Actual Behavior:

We're currently using the 2019 population estimates for counties.

Expected behavior

Should use the 2020 population estimates. It would be good to sanity check the new population file:

• deleted counties
• new counties
• check for large population changes (>10% ratio delta since 2019?)

Context

delphi_utils currently uses the 2019 FIPS population estimates from the Census, but looks like 2020 estimates have been available since April 1st. The 2019 estimates still used the pre-split county, but 2020 provides pop estimates for the new ones.

From here.

[dshemetov]

Some sanity checks results between the 2019 population data (current) and the 2020 population data.

Counties deleted:  {'02261'}
Counties added:  {'02063', '02066'}
Maximum percentile change in a county: 0.128
98% quantile change in a county: 0.037

The deleted and added counties are exactly and only the Alaska counties we need to change.

The distribution of population changes seems reasonable also: