remove '&' from URL patterns

'/?&#' -> '/?#' and '?&#' -> '?#'

According to https://www.ietf.org/rfc/rfc3986.txt, URLs are
"organized hierarchically" by using "the slash ("/"), question
mark ("?"), and number sign ("#") characters to delimit components"

gallery_dl/extractor/speakerdeck.py

@@ -20,7 +20,7 @@ class SpeakerdeckPresentationExtractor(Extractor):
     filename_fmt = "{presentation}-{num:>02}.{extension}"
     archive_fmt = "{presentation}_{num}"
     pattern = (r"(?:https?://)?(?:www\.)?speakerdeck\.com"
-               r"/([^/?&#]+)/([^/?&#]+)")
+               r"/([^/?#]+)/([^/?#]+)")
     test = (
         (("https://speakerdeck.com/speakerdeck/introduction-to-speakerdeck"), {
             "pattern": r"https://files.speakerdeck.com/presentations/"