settings: Don't mention username in fetch API key error message.

There isn't a username prompt in the form for it, so the only
possibility for triggering this error is a wrong password.

Fixes #20924.

zerver/tests/test_auth_backends.py

@@ -4345,7 +4345,7 @@ class JSONFetchAPIKeyTest(ZulipTestCase):
         user = self.example_user("hamlet")
         self.login_user(user)
         result = self.client_post("/json/fetch_api_key", dict(password="wrong"))
-        self.assert_json_error(result, "Your username or password is incorrect.", 400)
+        self.assert_json_error(result, "Password is incorrect.", 400)
 
     def test_invalid_subdomain(self) -> None:
         username = "hamlet"

zerver/tests/test_decorators.py

@@ -1143,7 +1143,7 @@ class FetchAPIKeyTest(ZulipTestCase):
     def test_fetch_api_key_wrong_password(self) -> None:
         self.login("cordelia")
         result = self.client_post("/json/fetch_api_key", dict(password="wrong_password"))
-        self.assert_json_error_contains(result, "password is incorrect")
+        self.assert_json_error_contains(result, "Password is incorrect")
 
 
 class InactiveUserTest(ZulipTestCase):

zerver/views/auth.py

@@ -977,7 +977,7 @@ def json_fetch_api_key(
         if not authenticate(
             request=request, username=user_profile.delivery_email, password=password, realm=realm
         ):
-            raise JsonableError(_("Your username or password is incorrect."))
+            raise JsonableError(_("Password is incorrect."))
 
     api_key = get_api_key(user_profile)
     return json_success({"api_key": api_key, "email": user_profile.delivery_email})