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

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

gallery_dl/extractor/pornpics.py

@@ -62,7 +62,7 @@ class PornpicsGalleryExtractor(PornpicsExtractor, GalleryExtractor):
     example = "https://www.pornpics.com/galleries/TITLE-12345/"
 
     def __init__(self, match):
-        url = "{}/galleries/{}/".format(self.root, match[1])
+        url = f"{self.root}/galleries/{match[1]}/"
         GalleryExtractor.__init__(self, match, url)
 
     items = GalleryExtractor.items
@@ -98,7 +98,7 @@ class PornpicsTagExtractor(PornpicsExtractor):
     example = "https://www.pornpics.com/tags/TAGS/"
 
     def galleries(self):
-        url = "{}/tags/{}/".format(self.root, self.groups[0])
+        url = f"{self.root}/tags/{self.groups[0]}/"
         return self._pagination(url)