plugins.euronews: fix live stream API URL scheme
plugins.euronews: fix live stream API URL scheme

Fixes #2047

chhe/streamlink,chhe/streamlink,wlerin/streamlink,beardypig/streamlink,streamlink/streamlink,back-to/streamlink,streamlink/streamlink,beardypig/streamlink,back-to/streamlink,bastimeyer/streamlink,bastimeyer/streamlink,melmorabity/streamlink,melmorabity/streamlink,wlerin/streamlink,gravyboat/streamlink,gravyboat/streamlink