gnu: webkitgtk-with-libsoup2: Use propagated inputs from GTK3.

This fixes an error in commits ee748c1df0 and
9bac1cad27, the latter of which was missing a
hunk to address the failing build of the former.
See <https://bugs.gnu.org/66480#47> for the full patch.

* gnu/packages/webkit.scm (webkitgtk-with-libsoup2)[propagated-inputs]: Use
package-propagated-inputs from webkitgtk-for-gtk3 rather than webkitgtk.

Co-authored-by: Vivien Kraus <vivien@planete-kraus.eu>

gnu/packages/webkit.scm

@@ -308,7 +308,7 @@ propagated by default) such as @code{gst-plugins-good} and
                  ((#:configure-flags flags)
                   #~(cons "-DUSE_SOUP2=ON" #$flags))))
     (propagated-inputs
-     (modify-inputs (package-propagated-inputs webkitgtk)
+     (modify-inputs (package-propagated-inputs webkitgtk-for-gtk3)
        (replace "libsoup" libsoup-minimal-2)))))
 
 (define-public wpewebkit