Fix multihash API usage and correct newsfragment issue number

- Fix multihash.encode() to multihash.digest().encode() in tests
- Rename newsfragment from 97.feature.rst to 181.feature.rst to match issue #181
- All tests now pass with correct multihash API usage

Author: acul71

newsfragments/97.feature.rst newsfragments/181.feature.rstnewsfragments/97.feature.rst renamed to newsfragments/181.feature.rst

@@ -373,7 +373,7 @@ def test_ipcidr_invalid_bytes_inputs():
 
 # --------CERT-HASH---------
 
-VALID_MULTIHASH_BYTES = multihash.encode(b"hello world", "sha2-256")
+VALID_MULTIHASH_BYTES = multihash.digest(b"hello world", "sha2-256").encode()
 VALID_CERTHASH_STRING = multibase.encode("base64url", VALID_MULTIHASH_BYTES).decode("utf-8")
 
 INVALID_BYTES = b"this is not a multihash"