Tooltip examples should be made keyboard accessible

[jessiehuff]

Describe the issue. What is the expected and unexpected behavior?
When an experience can be initiated by mouse, a similar experience should be provided to keyboard and assistive technology users. Currently the first two tooltip examples are not keyboard accessible.

Please provide the steps to reproduce. Feel free to link CodeSandbox or another tool.
Tab through the tooltips documentation, the first two examples do not show the tooltip because they are text and text does not normally receive focus. These spans should have a tabIndex in order to allow them to receive focus.

Is this a bug or enhancement? If this issue is a bug, is this issue blocking you or is there a work-around?
This is an example bug.

[jessiehuff]

It looks like this change got accidentally reverted in one of our merges into master from release: https://github.com/patternfly/patternfly-react/pull/4123/files?file-filters%5B%5D=.md#diff-dbcf37813f42d8c8ac6f747fe5aad7bcR40