Update license for sse.js

src/invidious/views/licenses.ecr

@@ -71,7 +71,7 @@
             </td>
 
             <td>
-                <a href="http://www.jclark.com/xml/copying.txt">Expat</a>
+                <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache-2.0-only</a>
             </td>
 
             <td>