README: Link to GitLab Issues instead of New Issue URL

When not logged in, the New Issue URL only redirects to an unhelpful
login page while the Issues page allows you to search for existing
issues and still offers a "New Issue" button.

Author: aklapper

README

@@ -10,4 +10,4 @@ and a GNOME GProxyResolver that uses the proxy information from the GSettings
 schemas in gsettings-desktop-schemas.
 
 File bugs against
-https://gitlab.gnome.org/GNOME/glib-networking/issues/new
+https://gitlab.gnome.org/GNOME/glib-networking/-/issues/