Corrected a typo with MultipleTextStringConfiguration class name

@zpqrtbnk approved in person this at CGRT18 ;-)

src/Umbraco.Web/PropertyEditors/MultipleTextStringConfiguration.cs

@@ -0,0 +1,14 @@
+namespace Umbraco.Web.PropertyEditors
+{
+    /// <summary>
+    /// Represents the configuration for a multiple textstring value editor.
+    /// </summary>
+    public class MultipleTextStringConfiguration
+    {
+        // fields are configured in the editor
+
+        public int Minimum { get; set; }
+
+        public int Maximum {get; set; }
+    }
+}