Correct error in metadata test

It should not be possible to have two signals with the same source,
signal, time_type, and geo_type. This will cause a query for that signal
to have two metadata rows attached to the covidcast_signal data frame,
which will confuse everything.

Author: capnrefsmmat

R-packages/covidcast/tests/testthat/api.covidcast.cmu.edu/epidata/api.php-dd024f.csv

@@ -1,3 +1,3 @@
 data_source,signal,time_type,geo_type,min_time,max_time,min_value,max_value,max_issue
 foo,bar,day,county,20200101,20200102,0,10,20200404
-foo,bar,day,county,20201002,20201003,0,10,20201101
+foo,bar,day,state,20201002,20201003,0,10,20201101

R-packages/covidcast/tests/testthat/test-covidcast.R

@@ -29,7 +29,7 @@ with_mock_api({
                      data_source = "foo",
                      signal = "bar",
                      time_type = "day",
-                     geo_type = "county",
+                     geo_type = c("county", "state"),
                      min_time = as.Date(c("2020-01-01", "2020-10-02")),
                      max_time = as.Date(c("2020-01-02", "2020-10-03")),
                      min_value = 0,