[skip release] Update CHANGELOG

Get rid of the cruft in the CHANGELOG created by the switch to
semantic-release.

Author: apotterri

CHANGELOG.md

@@ -10,12 +10,6 @@
 
 * Add appmap-agent-validate ([9f8da52](https://github.com/applandinc/appmap-python/commit/9f8da520b45ff511c8a55ac621d36321fb317d31))
 
-# Changelog
-All notable changes to this project will be documented in this file.
-
-The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
-and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
-
 ## [1.2.1] - 2021-09-24
 ### Added
 - The `appmap-agent-init` and `appmap-agent-status` internal commands are now available
@@ -27,7 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [#128] The error message for a missing config file now shows the full path where the
   file was expected to be found.
 
-## [1.2.0] - 2021-09-24
+## 1.2.0 - 2021-09-24
 - Pulled
 
 ## [1.1.0] - 2021-06-08