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/tumblr.py

@@ -295,7 +295,7 @@ class TumblrPostExtractor(TumblrExtractor):
 class TumblrTagExtractor(TumblrExtractor):
     """Extractor for images from a tumblr-user by tag"""
     subcategory = "tag"
-    pattern = BASE_PATTERN + r"/tagged/([^/?&#]+)"
+    pattern = BASE_PATTERN + r"/tagged/([^/?#]+)"
     test = ("http://demo.tumblr.com/tagged/Times%20Square", {
         "pattern": (r"https://\d+\.media\.tumblr\.com/tumblr_[^/_]+_1280.jpg"),
         "count": 1,