Replace FSF address with URL

Author: zeha

debian/copyright

@@ -19,9 +19,8 @@ Copyright:
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this package; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
-   02110-1301, USA.
+   along with this package; if not, go to
+   https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 
 On Debian GNU/Linux systems, the complete text of the GNU General
 Public License can be found in `/usr/share/common-licenses/GPL-2'.