Update broken URL in watch file

The software itself is now available from:

  http://www.codepad.de/en/download/firefox-add-ons/telify.html

tools/build-system/launchpad/mozilla-telify-sflphone/debian/watch

 version=3
-http://www.codepad.de/en/telify.html /download/telify-(.*)-fx.xpi
+http://www.codepad.de/en/download/firefox-add-ons/telify.html /download/Telify-(.*)-fx-tb.xpi