x/website: new drop-down menus block playground buttons

[findleyr]

It looks like new menus were added to go.dev in https://go.dev/cl/435522 -- nice.

However, @adonovan and I also noticed that it is easy to accidentally engage the menu when trying to click on 'Run' in the playground. Can this be improved? Happy to live with it if others don't find it bothersome.

(unfortunately my cursor is hidden by my recording software in the gif below)

[hyangah]

I'd like the menus appear only when "Docs" is clicked, not when I (accidentally) hover over "Docs".

[gopherbot]

Change https://go.dev/cl/447998 mentions this issue: _content/css: improve playground page margins