add dimensions section

Author: jaredsnyder

opmon/fr-billboard-rollout.toml

@@ -17,7 +17,7 @@ skip_default_metrics=true
 
 data_source = "newtab_clients_daily"
 boolean_pref = "mozfun.map.get_key(experiments, 'fr-billboard-rollout').branch IS NOT NULL"
-dimensions=['country']
+dimensions=['country_code']
 
 [metrics.organic_pocket_impressions.statistics]
 mean = {}
@@ -40,6 +40,6 @@ mean = {}
 mean = {}
 
 [dimensions]
-[dimensions.country]
+[dimensions.country_code]
 data_source = "newtab_clients_daily"
-select_expression = "country"
+select_expression = "country_code"