replace 2-element f-strings with simple '+' concatenations

Python's 'ast' module and its 'NodeVisitor' class
were incredibly helpful in identifying these

gallery_dl/extractor/schalenetwork.py

@@ -64,7 +64,7 @@ class SchalenetworkExtractor(Extractor):
 
     def _token(self, required=True):
         if token := self.config("token"):
-            return f"Bearer {token.rpartition(' ')[2]}"
+            return "Bearer " + token.rpartition(' ')[2]
         if required:
             raise exception.AuthRequired("'token'", "your favorites")
 
@@ -172,7 +172,7 @@ class SchalenetworkGalleryExtractor(SchalenetworkExtractor, GalleryExtractor):
         if self.config("cbz", False):
             headers["Authorization"] = self._token()
             dl = self.request_json(
-                f"{url}&action=dl", method="POST", headers=headers)
+                url + "&action=dl", method="POST", headers=headers)
             # 'crt' parameter here is necessary for 'hdoujin' downloads
             url = f"{dl['base']}?crt={self._crt()}"
             info = text.nameext_from_url(url)
@@ -259,7 +259,7 @@ class SchalenetworkFavoriteExtractor(SchalenetworkExtractor):
         params = text.parse_query(self.groups[1])
         params["page"] = text.parse_int(params.get("page"), 1)
         self.headers["Authorization"] = self._token()
-        return self._pagination(f"/books/favorites?crt={self._crt()}", params)
+        return self._pagination("/books/favorites?crt=" + self._crt(), params)
 
 
 SchalenetworkExtractor.extr_class = SchalenetworkGalleryExtractor