test(pdf): replace wildcard super import in registration_tests

Resolves SonarCloud rust:S2208 (new code).

crates/pdf/src/registration_tests.rs

@@ -1,4 +1,7 @@
-use super::*;
+use super::{
+    Affine, Arc, AssetId, BookletOptions, Cache, Content, Document, Item, PdfOptions, Rect, SpreadRef, Standard, export_booklet, export_pdf,
+    merge_pdfs,
+};
 
 fn placed_document(source: Vec<u8>) -> Document {
     use designcraft_doc::{Asset, Graphic, ItemId, Shape};