After PatternFly5 update: Snippets in Quick starts aren't readable in dark mode

Issue 57 from https://docs.google.com/spreadsheets/d/1TR3ENY-GE_LQL9F-xH6NahtRHdu6IrYGhLqDDA8y0EI/edit#gid=1035185624

Open the "Add Helm Chart Repositories to extend the Developer Catalog for your project" quick start. Go to the next step. You will see a code sample that does not have the right style if you've enabled dark theme.

Note: Could we check if we can also update the PatternFly quickstart extension??

Screenshot: https://drive.google.com/file/d/1hxh5VI2S7jLKRdNlDQsdlAXL_G7TxtME/view?usp=sharing