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/subscribestar.py

@@ -135,7 +135,7 @@ class SubscribestarExtractor(Extractor):
 class SubscribestarUserExtractor(SubscribestarExtractor):
     """Extractor for media from a subscribestar user"""
     subcategory = "user"
-    pattern = BASE_PATTERN + r"/(?!posts/)([^/?&#]+)"
+    pattern = BASE_PATTERN + r"/(?!posts/)([^/?#]+)"
     test = (
         ("https://www.subscribestar.com/subscribestar", {
             "count": ">= 20",