Merge bitcoin/bitcoin#29518: doc: correct function name in AssumeUTXO design docs

efb70cd doc: correct function name in AssumeUTXO design docs (jrakibi)

Pull request description:

  Corrected the function name from `CompleteSnapshotValidation()` to `MaybeCompleteSnapshotValidation()` in the assumeutxo design documentation.
  This change ensures that the documentation accurately reflects the actual function name used in the code

ACKs for top commit:
  Empact:
    ACK bitcoin/bitcoin@efb70cd

Tree-SHA512: 68b9be3ba710d91a2a955189e227f86b46ccb6a2a13c345d46f276cec6ff12b77ebf9814c4bcb00db7c17e221510e4a2e71175c78a6faf0e0e3159c761bc9b94

Author: fanquake

doc/design/assumeutxo.md

@@ -21,7 +21,7 @@ minimum and uses at least 1100 MiB.
 
 As the background sync continues there will be temporarily two chainstate
 directories, each multiple gigabytes in size (likely growing larger than the
-the downloaded snapshot).
+downloaded snapshot).
 
 ### Indexes
 
@@ -145,7 +145,7 @@ sequentially.
 
 Once the tip of the background chainstate hits the base block of the snapshot
 chainstate, we stop use of the background chainstate by setting `m_disabled`, in
-`CompleteSnapshotValidation()`, which is checked in `ActivateBestChain()`). We hash the
+`MaybeCompleteSnapshotValidation()`, which is checked in `ActivateBestChain()`). We hash the
 background chainstate's UTXO set contents and ensure it matches the compiled value in
 `CMainParams::m_assumeutxo_data`.