replace old %-formatted and .format(…) strings with f-strings (#7671)

mostly using flynt
https://github.com/ikamensh/flynt

gallery_dl/extractor/wikimedia.py

@@ -27,8 +27,9 @@ class WikimediaExtractor(BaseExtractor):
         if self.category == "wikimedia":
             self.category = self.root.split(".")[-2]
         elif self.category in ("fandom", "wikigg"):
-            self.category = "{}-{}".format(
-                self.category, self.root.partition(".")[0].rpartition("/")[2])
+            self.category = (
+                f"{self.category}-"
+                f"{self.root.partition('.')[0].rpartition('/')[2]}")
 
         self.per_page = self.config("limit", 50)