Revise "Sticky Posts" control help text to be more concise and accurate

[richtabor]

The current copy for the "Sticky Posts" control in the Query Loop block states:

Blog posts can be “stickied”, a feature that places them at the top of the front page of posts, keeping it there until new sticky posts are published.

However, this is inaccurate. Multiple sticky posts can be stuck at the same time—it's not only the latest sticky post.

We should update this text to also be much more concise, not unlike #63739.

Visual

See multiple sticky posts stuck to the top of the index:

[richtabor]

Component wise, there may be a better way to execute this control — but perhaps that's a separate issue.