* gnu/packages/gtk.scm (guile-rsvg): Update to commit 05c6a2fd.
[source](url): Change to gitlab.com.
(snippet): Use @GUILE_EFFECTIVE_VERSION@ instead of "2.0".
* gnu/packages/patches/guile-rsvg-pkgconfig.patch: Use
"$GUILE_EFFECTIVE_VERSION" instead of "2.0".