[generic] The url in the <meta redirect> doesn't need to be enclosed in single quotes (fixes #3770)

See the examples in https://en.wikipedia.org/wiki/Meta_refresh or the shortened urls from https://t.co/.

youtube_dl/extractor/generic.py

@@ -877,7 +877,7 @@ class GenericIE(InfoExtractor):
         if not found:
             found = re.search(
                 r'(?i)<meta\s+(?=(?:[a-z-]+="[^"]+"\s+)*http-equiv="refresh")'
-                r'(?:[a-z-]+="[^"]+"\s+)*?content="[0-9]{,2};url=\'([^\']+)\'"',
+                r'(?:[a-z-]+="[^"]+"\s+)*?content="[0-9]{,2};url=\'?([^\'"]+)',
                 webpage)
             if found:
                 new_url = found.group(1)