Update finger gestures documentation for GNOME 40

• https://gitlab.gnome.org/GNOME/gnome-user-docs/raw/master/gnome-help/C/figures/4-finger-drag.svg
• https://gitlab.gnome.org/GNOME/gnome-user-docs/blob/master/gnome-help/C/touchscreen-gestures.page

<andre> as I don't have a touchscreen device anymore: The four finger gesture to switch the workspace is now Dragging left or right (instead of up or down)?
<AlexanderMikhaylenko> yes
<AlexanderMikhaylenko> yeah, the code agrees, it was changed for both
<andre> so it's 3 fingers *to left or right* to go to another workspace in 40?
<AlexanderMikhaylenko> Yes, and upwards to open overview
<AlexanderMikhaylenko> Instead of the 3finger pinch