message: Update changelog for 1.23.1
diff: * Renaming symbol fails within a file that had recently been renamed without saving changes.
  * As a workaround, make an edit within the file before using Rename Symbol.
  -## 1.23.0 (Not yet released)
  +## 1.23.1 (Not yet released)
  +* Register FixAll commands for disposal ([#3984](https://github.com/OmniSharp/omnisharp-vscode/issues/3984), PR: [#3985](https://github.com/OmniSharp/omnisharp-vscode/pull/3985))
  +
  +## 1.23.0 (August 14, 2020)
  * Fix typo in supressBuildAssetsNotification setting name ([#3941](https://github.com/OmniSharp/omnisharp-vscode/issues/3941), PR: [#3942](https://github.com/OmniSharp/omnisharp-vscode/pull/3942))
  * Introduced a new `/quickinfo` endpoint to provide a richer set of information compared to `/typeinfo`. Consumers are encouraged to use it as their hover provider ([omnisharp-roslyn#1808](https://github.com/OmniSharp/omnisharp-roslyn/issues/1808), PR: [omnisharp-roslyn#1860](https://github.com/OmniSharp/omnisharp-roslyn/pull/1860)
  * Added support for Roslyn `EmbeddedLanguageCompletionProvider` which enables completions for string literals for `DateTime` and `Regex` ([omnisharp-roslyn#1871](https://github.com/OmniSharp/omnisharp-roslyn/pull/1871))
  