chore: add changelog entry under UNRELEASED tests

Signed-off-by: Shravya Jallepally <jallepally0.0shravya@gmail.com>

Author: shrav-jally

CHANGELOG.md

@@ -4,9 +4,10 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org).
 This changelog is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
-## [Unreleased]
+## [UNRELEASED]
 
 ### Tests
+- Formatted `ethereum_transaction_test.py` using Black.
 - Format account test files with Black (#1519)
 - Improve unit test coverage for `Hbar`, including edge cases, validation, comparisons, and hashing. (#1483)