Fix user_agent issue in save/delete (crash)

Author: gmazoyer

pyixapi/core/response.py

@@ -298,7 +298,7 @@ def save(self) -> bool:
                 base=self.endpoint.url,
                 token=self.api.access_token,
                 http_session=self.api.http_session,
-                user_agent=self.user_agent,
+                user_agent=self.api.user_agent,
                 proxies=self.api.proxies,
             )
             if r.patch(updates):
@@ -326,7 +326,7 @@ def delete(self) -> bool:
             base=self.endpoint.url,
             token=self.api.access_token,
             http_session=self.api.http_session,
-            user_agent=self.user_agent,
+            user_agent=self.api.user_agent,
             proxies=self.api.proxies,
         )
         return True if r.delete() else False