Fix channel edits on webhooks sending two requests

Author: Rapptz

discord/webhook/async_.py

@@ -1511,8 +1511,7 @@ async def edit(
                 proxy_auth=self.proxy_auth,
                 reason=reason,
             )
-
-        if prefer_auth and self.auth_token:
+        elif prefer_auth and self.auth_token:
             data = await adapter.edit_webhook(
                 self.id,
                 self.auth_token,

discord/webhook/sync.py

@@ -835,8 +835,7 @@ def edit(
 
             payload['channel_id'] = channel.id
             data = adapter.edit_webhook(self.id, self.auth_token, payload=payload, session=self.session, reason=reason)
-
-        if prefer_auth and self.auth_token:
+        elif prefer_auth and self.auth_token:
             data = adapter.edit_webhook(self.id, self.auth_token, payload=payload, session=self.session, reason=reason)
         elif self.token:
             data = adapter.edit_webhook_with_token(self.id, self.token, payload=payload, session=self.session, reason=reason)