Fix generation of imports for error mapping

Both import and location of usage must use toFirstCharacterUpperCase() to match.

src/Kiota.Builder/Writers/Python/CodeMethodWriter.cs

@@ -562,7 +562,7 @@ private void WriteRequestExecutorBody(CodeMethod codeElement, RequestParams requ
             writer.StartBlock($"{errorMappingVarName}: Dict[str, ParsableFactory] = {{");
             foreach (var errorMapping in codeElement.ErrorMappings)
             {
-                writer.WriteLine($"\"{errorMapping.Key.ToUpperInvariant()}\": {errorMapping.Value.Name},");
+                writer.WriteLine($"\"{errorMapping.Key.ToUpperInvariant()}\": {errorMapping.Value.Name.ToFirstCharacterUpperCase()},");
             }
             writer.CloseBlock();
         }