[epiphany/mcatanzaro/tech-preview-gtk4] Switch Tech Preview to use GTK 4 branch

[Michael Catanzaro <mcatanzaro src gnome org>]

commit b45d82574db500e1c2bf1c3ac1954ecd18b1eab8
Author: Michael Catanzaro <mcatanzaro redhat com>
Date:   Wed Mar 23 09:45:30 2022 -0500

    Switch Tech Preview to use GTK 4 branch
    
    This will allow some extra testing for the GTK 4 branch before we pull
    the trigger to merge it into master. It's a lot easier to revert this
    commit than it is to revert such a merge.

 org.gnome.Epiphany.json | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/org.gnome.Epiphany.json b/org.gnome.Epiphany.json
index 78ef33483..4a00c1eb4 100644
--- a/org.gnome.Epiphany.json
+++ b/org.gnome.Epiphany.json
@@ -127,6 +127,7 @@
                 {
                     "type" : "git",
                     "url" : "https://gitlab.gnome.org/GNOME/epiphany.git";,
+                    "branch" : "wip/exalm/gtk4",
                     "disable-shallow-clone" : true
                 }
             ]