Cleanup: Avoid unnecessary/annoying type alias in asset system

A `using FooPtr = std::unique_ptr<Foo>` isn't that useful usually, just
saves a few character stokes. It obfuscates the underlying type, which
is usually relevant information. Plus, `Ptr` for a unique pointer is
misleading (should be `UPtr` or similar).

source/blender/asset_system/intern/asset_library_service.hh

@@ -31,16 +31,14 @@ namespace blender::asset_system {
  *   loaded from a file on disk).
  */
 class AssetLibraryService {
-  using AssetLibraryPtr = std::unique_ptr<AssetLibrary>;
-
   static std::unique_ptr<AssetLibraryService> instance_;
 
   /* Mapping absolute path of the library's top-level directory to the AssetLibrary instance. */
-  Map<std::string, AssetLibraryPtr> on_disk_libraries_;
+  Map<std::string, std::unique_ptr<AssetLibrary>> on_disk_libraries_;
   /** Library without a known path, i.e. the "Current File" library if the file isn't saved yet. If
    * the file was saved, a valid path for the library can be determined and #on_disk_libraries_
    * above should be used. */
-  AssetLibraryPtr current_file_library_;
+  std::unique_ptr<AssetLibrary> current_file_library_;
 
   /* Handlers for managing the life cycle of the AssetLibraryService instance. */
   bCallbackFuncStore on_load_callback_store_;