Use assert_eq for encoded data length check

According to the Rust docs for `debug_assert` it should only be used if
there a proved performance costs to using `assert`.

Checking the length of a vector is fast, therefore its unlikely that
using `assert_eq` will have any noticeable performance costs.

src/consensus/encode.rs

@@ -140,7 +140,7 @@ impl From<psbt::Error> for Error {
 pub fn serialize<T: Encodable + ?Sized>(data: &T) -> Vec<u8> {
     let mut encoder = Vec::new();
     let len = data.consensus_encode(&mut encoder).expect("in-memory writers don't error");
-    debug_assert_eq!(len, encoder.len());
+    assert_eq!(len, encoder.len());
     encoder
 }