wallet, rpc: listdescriptors does not need unlocked

With the last hardened xpub cache, we don't neeed to have the wallet be
unlocked for listdescriptors.

src/wallet/rpcdump.cpp

@@ -1787,8 +1787,6 @@ RPCHelpMan listdescriptors()
         throw JSONRPCError(RPC_WALLET_ERROR, "listdescriptors is not available for non-descriptor wallets");
     }
 
-    EnsureWalletIsUnlocked(*wallet);
-
     LOCK(wallet->cs_wallet);
 
     UniValue descriptors(UniValue::VARR);