Use the anonymous lifetime for path

Lint error from new nightly "lifetime flowing from input to output with
different syntax can be confusing".

Add the anonymous lifetime to make it explicit.

bitcoin/src/blockdata/transaction.rs

@@ -309,7 +309,7 @@ pub trait TransactionExt: sealed::Sealed {
     /// This is useful in combination with [`predict_weight`] if you have the transaction already
     /// constructed with a dummy value in the fee output which you'll adjust after calculating the
     /// weight.
-    fn script_pubkey_lens(&self) -> TxOutToScriptPubkeyLengthIter;
+    fn script_pubkey_lens(&self) -> TxOutToScriptPubkeyLengthIter<'_>;
 
     /// Counts the total number of sigops.
     ///