Fix broken URL (fixes #1427)

doc/sphinxdoc/_templates/documentation.html

@@ -7,7 +7,7 @@ <h1>Essentia {{version}} Documentation</h1>
     <h2>What is Essentia?</h2>
 
     <p>Essentia is an open-source C++ library with Python and JavaScript bindings for <strong>audio analysis and audio-based music information retrieval</strong>. It is released
-    under the <strong><a href="http://tldrlegal.com/license/gnu-affero-general-public-license-v3-%28agpl-3.0%29#summary">Affero GPLv3
+    under the <strong><a href="https://www.tldrlegal.com/license/gnu-affero-general-public-license-v3-agpl-3-0">Affero GPLv3
     license</a></strong> and is also available under a proprietary license <a href="{{ pathto("licensing_information") }}">upon request</a>. The library contains an <strong><a href="{{ pathto("algorithms_overview") }}">
     extensive collection of reusable algorithms</a></strong> that implement audio input/output functionality, standard digital signal processing
     blocks, statistical characterization of data, and a large variety of spectral, temporal, tonal, and high-level music