Update CollectionShouldBeInDescendingOrder.cs

fix  missing parentheses in message

Author: jnyrup

src/FluentAssertions.BestPractices/Tips/Collections/CollectionShouldBeInDescendingOrder.cs

@@ -14,7 +14,7 @@ public class CollectionShouldBeInDescendingOrderAnalyzer : FluentAssertionsAnaly
         public const string DiagnosticId = Constants.Tips.Collections.CollectionShouldBeInDescendingOrder;
         public const string Category = Constants.Tips.Category;
 
-        public const string Message = "Use {0} .Should() followed by .BeInDescendingOrder instead.";
+        public const string Message = "Use {0} .Should() followed by .BeInDescendingOrder() instead.";
 
         protected override DiagnosticDescriptor Rule => new DiagnosticDescriptor(DiagnosticId, Title, Message, Category, DiagnosticSeverity.Info, true);
         protected override IEnumerable<FluentAssertionsCSharpSyntaxVisitor> Visitors