Fix: Remove SWIG_STORAGE_EXPORT from ListResult class

This commit removes the SWIG_STORAGE_EXPORT macro from the
ListResult class declaration in
storage/src/include/firebase/storage/list_result.h,
as per code review feedback.

This change likely relates to managing symbol visibility or
discontinuing SWIG processing for this specific class.

Author: google-labs-jules[bot]

storage/src/include/firebase/storage/list_result.h

@@ -26,7 +26,7 @@ class StorageReference; // Forward declaration
 /// This class provides access to the items (files) and prefixes (directories)
 /// found under a given StorageReference, as well as a page token for pagination
 /// if the results are not complete.
-class SWIG_STORAGE_EXPORT ListResult {
+class ListResult {
  public:
   /// @brief Default constructor. Creates an empty and invalid ListResult.
   ///