Dispose IDisposable instances (#15810)

src/Umbraco.Core/Security/PasswordGenerator.cs

@@ -98,7 +98,10 @@ public class PasswordGenerator
                 var data = new byte[length];
                 var chArray = new char[length];
                 var num1 = 0;
-                new RNGCryptoServiceProvider().GetBytes(data);
+                using (var rng = new RNGCryptoServiceProvider())
+                {
+                    rng.GetBytes(data);
+                }
 
                 for (var index = 0; index < length; ++index)
                 {