fixup! refactor(timeline): Make RoomDataProvider provide Decryptor to simplify redecryption

Correct error message when no decryptor is provided

Author: andybalaam

crates/matrix-sdk-ui/src/timeline/tests/mod.rs

@@ -479,7 +479,7 @@ impl Decryptor for TestRoomDataProvider {
     ) -> matrix_sdk::Result<TimelineEvent> {
         let Some(decryptor) = &self.decryptor else {
             panic!(
-                "No TestDecryptor supplied! Use TestTimelineBuilder::decryptor() to provide one."
+                "No TestDecryptor supplied! Use TestRoomDataProvider::with_decryptor to provide one."
             )
         };