[gtk/use-gtk-doc-for-gtk4: 1/2] Switch the gtk-doc subproject to the gtk-doc-for-gtk4 branch

[Matthias Clasen <matthiasc src gnome org>]

commit 906c3c570adabac71d884be5570f34b9805cf836
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Apr 13 16:40:11 2020 -0400

    Switch the gtk-doc subproject to the gtk-doc-for-gtk4 branch
    
    This branch contains assorted fixes and enhancements that
    are needed to build the gtk4 docs.

 subprojects/gtk-doc.wrap | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/subprojects/gtk-doc.wrap b/subprojects/gtk-doc.wrap
index 7469d027b0..0b8d4412d0 100644
--- a/subprojects/gtk-doc.wrap
+++ b/subprojects/gtk-doc.wrap
@@ -1,4 +1,4 @@
 [wrap-git]
 directory=gtk-doc
 url=https://gitlab.gnome.org/GNOME/gtk-doc.git
-revision=master
+revision=gtk-doc-for-gtk4