fix(popover/help/helpinfo): help button contains two button, it desactivate the default onKeyPress

[GuillaumeKESTEMAN]

Related issue

#1080

Description of the issue

I removed the second button to improve accessibility.
It wasn't blocking the onKeyPress but the condition which required your cursor to be over the button to use the onKeyPress.

I changed a little bit the UX :

Before :

Activated when :
- button click / button hover
- button hover + button focus+ press any key

Deactivated when :
- button click / no button hover
- click away from button
- button hover+ button focus+ press any key
- lose button focus

Now :

Activated when :
- button click / button hover
- button focus + press "Enter" key

Deactivated when :
- button click / no button hover
- click away from button
- button focus + press "Enter" key
- lose button focus

I had role="button" on PopoverOver wrapper to be focusable.

I've made a few styling changes, so if you have any questions/suggestions about this don't hesitate.

Person(s) for reviewing proposed changes

@samuel-gomez @MartinWeb

Important

Before creating a pull request run unit tests

$ npm test

# watch for changes
$ npm test -- --watch

# For a specific file (e.g., in packages/context/__tests__/command.test.js)
$ npm test -- --watch packages/action