Tabs on the extension registry are too small

Created by: felixfbecker

https://sourcegraph.com/extensions/sourcegraph/code-ownership

That change doesn't seem to have been part of the design: https://www.figma.com/file/7Ek89vyDoqlGhCn3wyS40J/11872-Extensions-discoverability-Final-review?node-id=477%3A6916