doc: Drop references to assumevalid in assumeutxo docs

doc/design/assumeutxo.md

@@ -1,7 +1,7 @@
 # assumeutxo
 
 Assumeutxo is a feature that allows fast bootstrapping of a validating bitcoind
-instance with a very similar security model to assumevalid.
+instance.
 
 The RPC commands `dumptxoutset` and `loadtxoutset` are used to
 respectively generate and load UTXO snapshots. The utility script

doc/release-notes-27596.md

@@ -12,7 +12,7 @@ RPC
 `loadtxoutset` has been added, which allows loading a UTXO snapshot of the format
 generated by `dumptxoutset`. Once this snapshot is loaded, its contents will be
 deserialized into a second chainstate data structure, which is then used to sync to
-the network's tip under a security model very much like `assumevalid`.
+the network's tip.
 
 Meanwhile, the original chainstate will complete the initial block download process in
 the background, eventually validating up to the block that the snapshot is based upon.

src/rpc/blockchain.cpp

@@ -2707,7 +2707,7 @@ static RPCHelpMan loadtxoutset()
         "Load the serialized UTXO set from disk.\n"
         "Once this snapshot is loaded, its contents will be "
         "deserialized into a second chainstate data structure, which is then used to sync to "
-        "the network's tip under a security model very much like `assumevalid`. "
+        "the network's tip. "
         "Meanwhile, the original chainstate will complete the initial block download process in "
         "the background, eventually validating up to the block that the snapshot is based upon.\n\n"