Making _immutableNonObjectTypesCache readonly

Author: MattyLeslie

src/Components/Components/src/ChangeDetection.cs

@@ -7,7 +7,7 @@ namespace Microsoft.AspNetCore.Components;
 
 internal sealed class ChangeDetection
 {
-    private static ConcurrentDictionary<Type, bool> _immutableNonObjectTypesCache = new();
+    private static readonly ConcurrentDictionary<Type, bool> _immutableNonObjectTypesCache = new();
     public static bool MayHaveChanged<T1, T2>(T1 oldValue, T2 newValue)
     {
         var oldIsNotNull = oldValue != null;