help-overlay: Remove "CTRL+S" and include "CTRL+F"
CTRL+S is no longer a shortcut to trigger search ever since !1609 (merged), because is a shortcut reserved for saving a file/content: https://developer.gnome.org/hig/reference/keyboard.html
Also, CTRL+F, which is the shortcut recommended by HIG to trigger search, already triggered the search bar in Settings prior to change that removed CTRL+S. However, this shortcut was absent from the shortcuts window.
Edited by Automeris naranja