Admin bar "About WordPress" empty link and title attributes

[afercia]

When checking accessibility issues with automated tools, e.g. the WAVE Evaluation Tool, there's always, in every admin screen, one error related to "empty link". Finally figured out it's the "About WordPress" toolbar top-level link which has no text, just a title attribute.
In the proposed patch I would propose to remove the title attribute and use its string as screen-reader-text.

Removed also two other title attributes:
'My Account'
'Add New'
didn't touch the Updates and Comments count ones. though the title attribute is a poorly implemented feature and not so useful, see #24766, maybe in the future a new UI feature should be used to display those data.

[SergeyBiryukov]

In 31456:

Toolbar: Remove title attributes from 'About WordPress', 'Add New', and 'My Account' items.

props afercia.
fixes #31324.