[francetv] Update to fix thumbnail URL issue (#27120)

Fix the thumbnail URL. The issue was here for many years, never fixed. It's done ! :-)

Example : https://www.france.tv/france-2/de-gaulle-l-eclat-et-le-secret/de-gaulle-l-eclat-et-le-secret-saison-1/2035247-solitude.html

failed thumbnail url generated : http://pluzz.francetv.fr/staticftv/ref_emissions/2020-11-02/EMI_1104da66f533cc7dc5d0d07a181a18c2e2fe1d81_20201014122553940.jpg

right thumbnail url fixed : https://sivideo.webservices.francetelevisions.fr/staticftv/ref_emissions/2020-11-02/EMI_1104da66f533cc7dc5d0d07a181a18c2e2fe1d81_20201014122553940.jpg

youtube_dl/extractor/francetv.py

@@ -211,7 +211,7 @@ class FranceTVIE(InfoExtractor):
             'id': video_id,
             'title': self._live_title(title) if is_live else title,
             'description': clean_html(info.get('synopsis')),
-            'thumbnail': urljoin('http://pluzz.francetv.fr', info.get('image')),
+            'thumbnail': urljoin('https://sivideo.webservices.francetelevisions.fr', info.get('image')),
             'duration': int_or_none(info.get('real_duration')) or parse_duration(info.get('duree')),
             'timestamp': int_or_none(try_get(info, lambda x: x['diffusion']['timestamp'])),
             'is_live': is_live,