SQLActivity page - make horizontal scrollbar always visible

[fabiog1901]

In the SQL Activity > Statement page, the horizontal scrollbar currently sits at the bottom of the list of statements. If the list is taller than the screen height, the scrollbar disappears from view. Ideally, it should be visible at all times to allow the user to scroll across.

Slack conversation for an image of the problem.

Jira issue: CRDB-32354