rpc: doc: drop descriptor wallet mentions in fast wallet rescan related RPCs

Now that we only ever operate on descriptor wallets, mentioning
that a faster rescan is only available for them is redundant and
can be removed.

These texts were originally introduced in commit
ca48a4694f (PR #25957).

src/wallet/rpc/backup.cpp

@@ -611,8 +611,8 @@ RPCHelpMan restorewallet()
     return RPCHelpMan{
         "restorewallet",
         "Restores and loads a wallet from backup.\n"
-        "\nThe rescan is significantly faster if a descriptor wallet is restored"
+        "\nThe rescan is significantly faster if block filters are available"
-        "\nand block filters are available (using startup option \"-blockfilterindex=1\").\n",
+        "\n(using startup option \"-blockfilterindex=1\").\n",
         {
             {"wallet_name", RPCArg::Type::STR, RPCArg::Optional::NO, "The name that will be applied to the restored wallet"},
             {"backup_file", RPCArg::Type::STR, RPCArg::Optional::NO, "The backup file that will be used to restore the wallet."},

src/wallet/rpc/transactions.cpp

@@ -857,8 +857,8 @@ RPCHelpMan rescanblockchain()
         "rescanblockchain",
         "Rescan the local blockchain for wallet related transactions.\n"
                 "Note: Use \"getwalletinfo\" to query the scanning progress.\n"
-                "The rescan is significantly faster when used on a descriptor wallet\n"
+                "The rescan is significantly faster if block filters are available\n"
-                "and block filters are available (using startup option \"-blockfilterindex=1\").\n",
+                "(using startup option \"-blockfilterindex=1\").\n",
                 {
                     {"start_height", RPCArg::Type::NUM, RPCArg::Default{0}, "block height where the rescan should start"},
                     {"stop_height", RPCArg::Type::NUM, RPCArg::Optional::OMITTED, "the last block height that should be scanned. If none is provided it will rescan up to the tip at return time of this call."},