mute user: Remove unnecessary check for double muting.

In 141b0c4, we added code to handle races caused by duplicate muting
requests. That code can also handle the non-race condition, so we don't
require the first check.

zerver/tests/test_muted_users.py

@@ -76,14 +76,6 @@ class MutedUsersTests(ZulipTestCase):
         result = self.api_post(hamlet, url)
         self.assert_json_error(result, "User already muted")
 
-        # Verify the error handling for the database level
-        # IntegrityError we'll get with a race between two processes
-        # trying to mute the user.  To do this, we patch the
-        # get_mute_object function to always return None.
-        with mock.patch("zerver.views.muted_users.get_mute_object", return_value=None):
-            result = self.api_post(hamlet, url)
-            self.assert_json_error(result, "User already muted")
-
     def _test_add_muted_user_valid_data(self, deactivate_user: bool = False) -> None:
         hamlet = self.example_user("hamlet")
         self.login_user(hamlet)

zerver/views/muted_users.py

@@ -20,9 +20,6 @@ def mute_user(request: HttpRequest, user_profile: UserProfile, muted_user_id: in
     )
     date_muted = timezone_now()
 
-    if get_mute_object(user_profile, muted_user) is not None:
-        raise JsonableError(_("User already muted"))
-
     try:
         do_mute_user(user_profile, muted_user, date_muted)
     except IntegrityError: