Set license type on about dialog

This ensures that the proper license is displayed on the about
dialog even if the license file is missing from the system.

Author: City-busz

usr/lib/webapp-manager/webapp-manager.py

@@ -238,13 +238,7 @@ def open_about(self, widget):
         dlg.set_title(_("About"))
         dlg.set_program_name(_("Web Apps"))
         dlg.set_comments(_("Run websites as if they were apps"))
-        try:
-            with open('/usr/share/common-licenses/GPL', encoding="utf-8") as h:
-                gpl = h.read()
-            dlg.set_license(gpl)
-        except Exception as e:
-            print(e)
-
+        dlg.set_license_type(Gtk.License.GPL_3_0)
         dlg.set_version("__DEB_VERSION__")
         dlg.set_icon_name("webapp-manager")
         dlg.set_logo_icon_name("webapp-manager")