Fix changelog release date for 1.9.8 (#9210)

Author: Colengms

Extension/CHANGELOG.md

@@ -1,6 +1,6 @@
 # C/C++ for Visual Studio Code Change Log
 
-## Version 1.9.8: March 20, 2022
+## Version 1.9.8: April 20, 2022
 ### Bug Fixes
 * Fix an issue with extension activation failing if `C_Cpp.intelliSenseEngine` was set to `Disabled`. [#9083](https://github.com/microsoft/vscode-cpptools/issues/9083)