chore: Change same enivornment to one hour

lib/utils/date_time_extension.dart

@@ -21,17 +21,10 @@ extension DateTimeExtension on DateTime {
     return millisecondsSinceEpoch <= other.millisecondsSinceEpoch;
   }
 
-  /// Two message events can belong to the same environment. That means that they
-  /// don't need to display the time they were sent because they are close
-  /// enaugh.
-  static const minutesBetweenEnvironments = 10;
-
   /// Checks if two DateTimes are close enough to belong to the same
   /// environment.
-  bool sameEnvironment(DateTime prevTime) {
-    return millisecondsSinceEpoch - prevTime.millisecondsSinceEpoch <
-        1000 * 60 * minutesBetweenEnvironments;
-  }
+  bool sameEnvironment(DateTime prevTime) =>
+      prevTime.difference(this) < const Duration(hours: 1);
 
   /// Returns a simple time String.
   String localizedTimeOfDay(BuildContext context) =>