htp: use transactions right get function

Not the VecDeque one

Ticket: 7803

rust/htp/src/transactions.rs

@@ -33,7 +33,7 @@ impl Transactions {
         // that transaction is started), or zero if neither
         // request or response transaction exist yet
         let tx_to_check = std::cmp::max(self.request, self.response);
-        match self.transactions.get(tx_to_check) {
+        match self.get(tx_to_check) {
             // Transaction is created, check if it is started
             Some(tx) => tx.index.wrapping_add(tx.is_started() as usize),
             // Transaction doesn't exist yet, so the index is the size