The title parameter lets you define a title to appear above the post listing. This uses the <h2> element by default. You can use the display_posts_shortcode_title_tag filter to modify what heading is used. The code below changes this to an h4.
Filter: display_posts_shortcode_title_tag
Modify what heading tag is used for display posts title if [[display-posts title="Recent Posts"]]. The default is h2.