Fix sonarcloud bug

Author: MaggieKimani1

src/Microsoft.OpenApi/Models/OpenApiParameter.cs

@@ -20,7 +20,7 @@ public class OpenApiParameter : IOpenApiSerializable, IOpenApiReferenceable, IEf
     {
         private bool? _explode;
         private ParameterStyle? _style;
-        private JsonSchema _schema;
+        protected JsonSchema _schema;
 
         /// <summary>
         /// Indicates if object is populated with data or is just a reference to the data

src/Microsoft.OpenApi/Models/References/OpenApiParameterReference.cs

@@ -84,7 +84,7 @@ public override string Description
         public override bool AllowReserved { get => Target.AllowReserved; set => Target.AllowReserved = value; }
 
         /// <inheritdoc/>
-        public override JsonSchema Schema { get => Target.Schema; set => Target.Schema = value; }
+        public override JsonSchema Schema { get => _schema; set => _schema = value; }
 
         /// <inheritdoc/>
         public override IDictionary<string, OpenApiExample> Examples { get => Target.Examples; set => Target.Examples = value; }