Update changelog

Author: aeisenberg

extensions/ql-vscode/CHANGELOG.md

@@ -28,6 +28,7 @@
 - Add a `View DIL` command on query history items. This opens a text editor containing the Datalog Intermediary Language representation of the compiled query.
 - Remove feature flag for the AST Viewer. For more information on how to use the AST Viewer, [see the documentation](https://help.semmle.com/codeql/codeql-for-vscode/procedures/exploring-the-structure-of-your-source-code.html).
 - The `codeQL.runningTests.numberOfThreads` setting is now used correctly when running tests.
+- Alter structure of the _Test Explorer_ tree. It now follows the structure of the filesystem instead of the qlpacks.
 
 ## 1.3.3 - 16 September 2020