chore: address PR feedback and add changelog entry

Author: jcnelson

CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to the versioning scheme outlined in the [README.md](RE
 
 - Miners who restart their nodes immediately before a winning tenure now correctly detect that
   they won the tenure after their nodes restart ([#5750](https://github.com/stacks-network/stacks-core/issues/5750)).
+- Error responses to /v2/transactions/fees are once again expressed as JSON ([#4145](https://github.com/stacks-network/stacks-core/issues/4145)).
 
 ## [3.1.0.0.4]
 

stackslib/src/net/api/tests/postfeerate.rs

@@ -122,7 +122,7 @@ fn test_try_make_response() {
     assert_eq!(preamble.status_code, 400);
     debug!("Response JSON no estimator: {}", &body_json);
 
-    // case 2: no estimate avaialable
+    // case 2: no estimate available
     let mut requests = vec![];
     let request = StacksHttpRequest::new_post_fee_rate(
         addr.clone().into(),