Fix example in fixture documentation (sending_user, receiving_user) (#9179)

AUTHORS

@@ -240,6 +240,7 @@ Petter Strandmark
 Philipp Loose
 Pieter Mulder
 Piotr Banaszkiewicz
+Piotr Dybowski
 Piotr Helm
 Prakhar Gurunani
 Prashant Anand

doc/en/fixture.rst

@@ -869,19 +869,19 @@ Here's what that might look like:
     def sending_user(mail_admin):
         user = mail_admin.create_user()
         yield user
-        admin_client.delete_user(user)
+        mail_admin.delete_user(user)
 
 
     @pytest.fixture
     def receiving_user(mail_admin):
         user = mail_admin.create_user()
         yield user
-        admin_client.delete_user(user)
+        mail_admin.delete_user(user)
 
 
-    def test_email_received(receiving_user, email):
+    def test_email_received(receiving_user, sending_user):
         email = Email(subject="Hey!", body="How's it going?")
-        sending_user.send_email(_email, receiving_user)
+        sending_user.send_email(email, receiving_user)
         assert email in receiving_user.inbox
 
 Because ``receiving_user`` is the last fixture to run during setup, it's the first to run