Update CHANGELOG.md for latest release

Author: dibarbet

CHANGELOG.md

@@ -11,7 +11,7 @@
 * Update Roslyn version to 4.9.0-1.23502.8 (PR: [#6447](https://github.com/dotnet/vscode-csharp/pull/6447))
   * Update Razor project configuration file name (PR: [#70156](https://github.com/dotnet/roslyn/pull/70156))
 
-## 2.5.?
+## 2.5.30
 * Update Roslyn version to 4.9.0-1.23502.2 (PR: [#6463](https://github.com/dotnet/vscode-csharp/pull/6463))
   * Fix issue loading projects on .NET 8 RC2 (PR: [#70196](https://github.com/dotnet/roslyn/pull/70196))
   * Fix exception thrown by outdated version of ExternalAccess.RazorCompiler.dll (PR: [#70716](https://github.com/dotnet/roslyn/pull/70176))