chore(library)!: drop the full-replace PUT of a backlog entry

The Frontend sends PATCH since item 27 batch 2.

readme.md

@@ -117,7 +117,6 @@ ArchUnit role rules (`RoleAnnotationRules`) and `src/test/resources/contract/aut
 |---|---|---|
 | `GET` | `/api/library/games`, `/api/library/games/{appid}` | JWT |
 | `PATCH` | `/api/library/games/{appid}/backlog` (only the sent fields; `null` clears one) | JWT |
-| `PUT` | `/api/library/games/{appid}/backlog` (replaces all four; removed in item 29) | JWT |
 | `PUT`, `DELETE` | `/api/library/games/{appid}/corrections/{field}` (`{value}`; `name`, `image`, `speedrun`, `moods`, `endless`, `genres`; `204`, `400 INVALID_CORRECTION`) | JWT, AUDITOR |
 | `POST` | `/api/library/games/{appid}/merge` (`{otherAppid}`; `200 {appid}` = the key that stays, `400 SAME_GAME` / `STEAM_GAMES`, `404 GAME_NOT_FOUND`) | JWT, AUDITOR |
 | `PUT` | `/api/library/games/{appid}/status` (status only, keeps rating, notes, priority) | JWT |