Fix the docblock for layout_suppress()

[indigoxela]

Description of the bug

This docblock is extremely misleading:

/**
 * Suppress the layout.
 *
 * This function should be called from within another module's page callback
 * when the layout should not be displayed, that is, content only. This can be
 * useful for modules that implement popup pages or other special pages where
 * the default layout would be distracting.
 *
 * @param bool $suppress
 *   If set to TRUE, the layout will be suppressed.
 *
 * @return bool
 *   TRUE if the layout can be suppressed, FALSE otherwise.
 *
 * @since 1.21.0 Function added.
 */

That's wrong. Calling layout_suppress inside a page callback does nothing.

Instead, it's necessary to use something like hook_init(), checking for the path, and calling layout_suppress() on desired paths.