Stop using deprecated to_vec

Recently we deprecated `to_vec` in favour of `to_bytes` however we
continued to use `to_vec` in a few places. This wasn't noticed because
of our usage of `TBD` in the `deprecated` attribute.

Use `to_bytes` instead of `to_vec`.

bitcoin/src/blockdata/transaction.rs

@@ -1786,7 +1786,7 @@ mod tests {
             .is_err());
 
         // test that we get a failure if we corrupt a signature
-        let mut witness: Vec<_> = spending.input[1].witness.to_vec();
+        let mut witness = spending.input[1].witness.to_bytes();
         witness[0][10] = 42;
         spending.input[1].witness = Witness::from_slice(&witness);
 

bitcoin/src/blockdata/witness.rs

@@ -775,7 +775,7 @@ mod test {
         let expected_witness = vec![hex!(
             "304402207c800d698f4b0298c5aac830b822f011bb02df41eb114ade9a6702f364d5e39c0220366900d2a60cab903e77ef7dd415d46509b1f78ac78906e3296f495aa1b1b54101")
             ];
-        assert_eq!(witness.to_vec(), expected_witness);
+        assert_eq!(witness.to_bytes(), expected_witness);
     }
 
     #[test]

bitcoin/src/crypto/ecdsa.rs

@@ -345,6 +345,6 @@ mod tests {
         let mut buf = vec![];
         sig.serialize_to_writer(&mut buf).expect("write failed");
 
-        assert_eq!(sig.to_vec(), buf)
+        assert_eq!(sig.to_bytes(), buf)
     }
 }

bitcoin/src/psbt/serialize.rs

@@ -172,7 +172,7 @@ impl Deserialize for secp256k1::PublicKey {
 }
 
 impl Serialize for ecdsa::Signature {
-    fn serialize(&self) -> Vec<u8> { self.to_vec() }
+    fn serialize(&self) -> Vec<u8> { self.to_bytes() }
 }
 
 impl Deserialize for ecdsa::Signature {
@@ -265,7 +265,7 @@ impl Deserialize for XOnlyPublicKey {
 }
 
 impl Serialize for taproot::Signature {
-    fn serialize(&self) -> Vec<u8> { self.to_vec() }
+    fn serialize(&self) -> Vec<u8> { self.to_bytes() }
 }
 
 impl Deserialize for taproot::Signature {