[gtk-web] Update links in index.md

[Emmanuele Bassi <ebassi src gnome org>]

commit 36c6c12d8179281c1e7813c9b42167e57215ac8b
Author: Emmanuele Bassi <ebassi gmail com>
Date:   Thu Mar 18 13:12:04 2021 +0000

    Update links in index.md
    
    We have had a stable release of GTK4, so we should link to its API reference.
    
    Fixes: #80

 _docs/apis/index.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/_docs/apis/index.md b/_docs/apis/index.md
index e270997c..dcd3eaa8 100644
--- a/_docs/apis/index.md
+++ b/_docs/apis/index.md
@@ -6,9 +6,9 @@ application development.
 
 ### User interface and display
 
- - [GTK](https://developer.gnome.org/gtk4/unstable/) — Widget toolkit for graphical interfaces
- - [GDK](https://developer.gnome.org/gdk4/unstable/) — Low-level abstraction for the windowing system
- - [GSK](https://developer.gnome.org/gsk4/unstable/) — Low-level scene graph and 3D rendering API
+ - [GTK](https://developer.gnome.org/gtk4/stable/) — Widget toolkit for graphical interfaces
+ - [GDK](https://developer.gnome.org/gdk4/stable/) — Low-level abstraction for the windowing system
+ - [GSK](https://developer.gnome.org/gsk4/stable/) — Low-level scene graph and 3D rendering API
  - [Cairo](https://developer.gnome.org/cairo/stable/) — 2D, vector-based drawing for high-quality graphics
  - [Pango](https://developer.gnome.org/pango/stable/) — International text rendering with full Unicode 
support
  - [ATK](https://developer.gnome.org/atk/stable/) — Accessibility toolkit to implement support for screen 
readers and other tools (GTK3 only)