metrics_container changes reverted since I didn't use any enumerable methods post refactor

Author: benngarcia

lib/prometheus_exporter/server/metrics_container.rb

@@ -2,8 +2,6 @@
 
 module PrometheusExporter::Server
   class MetricsContainer
-    # Since MetricsContainer defines #each, we can include Enumerable
-    include Enumerable
     METRIC_MAX_AGE = 60
     METRIC_EXPIRE_ATTR = "_expire_at"
 
@@ -40,6 +38,10 @@ def each(&blk)
       wrap_expire(:each, &blk)
     end
 
+    def map(&blk)
+      wrap_expire(:map, &blk)
+    end
+
     def expire(time: nil, new_metric: nil)
       time ||= get_time