remove @staticmethod decorators

There might have been a time when calling a static method was faster
than a regular method, but that is no longer the case. According to
micro-benchmarks, it is 70% slower in CPython 3.13 and it also makes
executing the code of a class definition slower.

gallery_dl/extractor/mangoxo.py

@@ -53,8 +53,7 @@ class MangoxoExtractor(Extractor):
             raise exception.AuthenticationError(data.get("msg"))
         return {"SESSION": self.cookies.get("SESSION")}
 
-    @staticmethod
-    def _sign_by_md5(username, password, token):
+    def _sign_by_md5(self, username, password, token):
         # https://dns.mangoxo.com/libs/plugins/phoenix-ui/js/phoenix-ui.js
         params = [
             ("username" , username),
@@ -68,8 +67,7 @@ class MangoxoExtractor(Extractor):
         params.append(("sign", sign.upper()))
         return params
 
-    @staticmethod
-    def _total_pages(page):
+    def _total_pages(self, page):
         return text.parse_int(text.extract(page, "total :", ",")[0])