Cleanup: remove 'this' keyword where guidelines don't ask for it

4cc1c65272 made this a protected member, so following the C++ style
guidelines, this doesn't have to use `this` for accessing.

source/blender/asset_system/intern/asset_library.cc

@@ -191,7 +191,7 @@ void AssetLibrary::load_catalogs()
 {
   auto catalog_service = std::make_unique<AssetCatalogService>(root_path());
   catalog_service->load_from_disk();
-  this->catalog_service_ = std::move(catalog_service);
+  catalog_service_ = std::move(catalog_service);
 }
 
 AssetCatalogService &AssetLibrary::catalog_service() const

source/blender/asset_system/intern/asset_library_all.cc

@@ -58,7 +58,7 @@ void AllAssetLibrary::rebuild_catalogs_from_nested(const bool reload_nested_cata
       },
       false);
 
-  this->catalog_service_ = std::move(new_catalog_service);
+  catalog_service_ = std::move(new_catalog_service);
   catalogs_dirty_ = false;
 }