[epiphany] flatpak: Set WEBKIT_NICOSIA_PAINTING_THREADS=0

[Alexander Mikhaylenko <alexm src gnome org>]

commit b2714c07998aa8720a4640b7830f444176e7fdc1
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Thu Mar 24 00:30:18 2022 +0400

    flatpak: Set WEBKIT_NICOSIA_PAINTING_THREADS=0
    
    For now we need it to get GTK4 WebKit to not break rendering on almost
    every page. We should remove it once it's fixed.

 org.gnome.Epiphany.json | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/org.gnome.Epiphany.json b/org.gnome.Epiphany.json
index c961c74d5..858a69f02 100644
--- a/org.gnome.Epiphany.json
+++ b/org.gnome.Epiphany.json
@@ -18,7 +18,8 @@
         "--socket=pulseaudio",
         "--socket=wayland",
         "--system-talk-name=org.freedesktop.GeoClue2",
-        "--own-name=org.gnome.Epiphany.WebAppProvider"
+        "--own-name=org.gnome.Epiphany.WebAppProvider",
+        "--env=WEBKIT_NICOSIA_PAINTING_THREADS=0"
     ],
     "modules" : [
          {