Resolve all high-severity architecture review findings

src/ZB.MOM.WW.ScadaBridge.DataConnectionLayer/Adapters/MxGatewayDataConnection.cs

@@ -263,7 +263,7 @@ public class MxGatewayDataConnection
     public async Task UnsubscribeAsync(string subscriptionId, CancellationToken cancellationToken = default)
     {
         if (_subs.TryRemove(subscriptionId, out var s))
-            _tagToSub.TryRemove(s.TagPath, out _);
+            ((ICollection<KeyValuePair<string, string>>)_tagToSub).Remove(new(s.TagPath, subscriptionId));
         await _client!.UnsubscribeAsync(subscriptionId, cancellationToken);
     }
 
@@ -297,7 +297,7 @@ public class MxGatewayDataConnection
         foreach (var id in subscriptionIds)
         {
             if (_subs.TryRemove(id, out var s))
-                _tagToSub.TryRemove(s.TagPath, out _);
+                ((ICollection<KeyValuePair<string, string>>)_tagToSub).Remove(new(s.TagPath, id));
         }
 
         await _client!.UnsubscribeBulkAsync(subscriptionIds, cancellationToken);