Mark GetAnnotationParams as obsolete (PSPDF Kit deprecated)

Added [Obsolete] attribute to GetAnnotationParams in ConfigController to indicate that PSPDF Kit will no longer be used and the method is deprecated. This warns developers to avoid using this method in future development.

EnvelopeGenerator.API/Controllers/ConfigController.cs

@@ -22,6 +22,7 @@ public class ConfigController(IOptionsMonitor<AnnotationParams> annotationParams
     /// Returns annotation configuration that was previously rendered by MVC.
     /// </summary>
     [HttpGet("Annotations")]
+    [Obsolete("PSPDF Kit will no longer be used.")]
     public IActionResult GetAnnotationParams()
     {
         return Ok(_annotationParams.AnnotationJSObject);