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

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

gallery_dl/extractor/speakerdeck.py

@@ -28,7 +28,7 @@ class SpeakerdeckPresentationExtractor(GalleryExtractor):
 
         url = self.root + "/oembed.json"
         params = {
-            "url": "{}/{}/{}".format(self.root, user, presentation),
+            "url": f"{self.root}/{user}/{presentation}",
         }
         data = self.request(url, params=params).json()
 
@@ -44,7 +44,7 @@ class SpeakerdeckPresentationExtractor(GalleryExtractor):
         }
 
     def images(self, _):
-        url = "{}/player/{}".format(self.root, self.presentation_id)
+        url = f"{self.root}/player/{self.presentation_id}"
         page = self.request(url).text
         page = util.re(r"\s+").sub(" ", page)
         return [