Remove comment referencing now-unused covidcast::county_census

vignettes/aggregation.Rmd

@@ -17,7 +17,7 @@ library(epidatr)
 library(epiprocess)
 library(dplyr)
 
-# Use covidcast::county_census to get the county and state names
+# Get mapping between FIPS codes and county&state names:
 y <- readr::read_csv("https://github.com/cmu-delphi/covidcast/raw/c89e4d295550ba1540d64d2cc991badf63ad04e5/Python-packages/covidcast-py/covidcast/geo_mappings/county_census.csv") %>% # nolint: line_length_linter
   filter(STNAME %in% c("Massachusetts", "Vermont"), STNAME != CTYNAME) %>%
   select(geo_value = FIPS, county_name = CTYNAME, state_name = STNAME)