style(core): use var where the type is apparent (IDE0007)

The JsonDocument.Parse result names its type on the RHS, so the repo convention
(csharp_style_var_when_type_is_apparent) wants var there. Clears the last Sonar smell.

Author: thiagoluga

src/NeoReports.Core/Configuration/JsonLogicFilter.cs

@@ -27,7 +27,7 @@ public static Func<ReportRecord, bool> Compile(string expression)
         JsonElement root;
         try
         {
-            using JsonDocument document = JsonDocument.Parse(expression);
+            using var document = JsonDocument.Parse(expression);
             root = document.RootElement.Clone();
         }
         catch (JsonException ex)