Fix errors in base styles css file.

Closes #3539627

Link to designs: https://www.figma.com/design/sLiIjn5ktrzDCZei5hpNJs/Drupal.org-Style-Guide-and-Official-Designs?node-id=10525-45366&t=I34eJYSqUYiRoBBE-0

Testing instructions

• Spin up this branch with the drupalorg main project checked out to main.
• Create a test landing page and add a text section, make sure that you set the editor to use full html.
• Add a test block quote. Verify that the styling matches the designs.
• Add some sample text and wrap some of it in small tags. Verify that the styling matches the designs.