[bugfix] return 422 for invalid status visibility (#4252)

Signed-off-by: nicole mikołajczyk <git@mkljczk.pl>

# Description

closes #4247

## Checklist

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- [x] I/we have read the [GoToSocial contribution guidelines](https://codeberg.org/superseriousbusiness/gotosocial/src/branch/main/CONTRIBUTING.md).
- [ ] I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
- [x] I/we have not leveraged AI to create the proposed changes.
- [x] I/we have performed a self-review of added code.
- [x] I/we have written code that is legible and maintainable by others.
- [ ] I/we have commented the added code, particularly in hard-to-understand areas.
- [ ] I/we have made any necessary changes to documentation.
- [x] I/we have added tests that cover new code.
- [x] I/we have run tests and they pass locally with the changes.
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Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4252
Co-authored-by: nicole mikołajczyk <git@mkljczk.pl>
Co-committed-by: nicole mikołajczyk <git@mkljczk.pl>

internal/api/client/statuses/statuscreate_test.go

@@ -446,7 +446,7 @@ func (suite *StatusCreateTestSuite) TestPostNewStatusIntPolicyJSON() {
 func (suite *StatusCreateTestSuite) TestPostNewStatusMessedUpIntPolicy() {
 	out, recorder := suite.postStatus(nil, `{
   "status": "this is a brand new status! #helloworld",
-  "visibility": "followers_only",
+  "visibility": "private",
   "interaction_policy": {
     "can_reply": {
       "always": [
@@ -463,7 +463,7 @@ func (suite *StatusCreateTestSuite) TestPostNewStatusMessedUpIntPolicy() {
 	// We should have a helpful error
 	// message telling us how we screwed up.
 	suite.Equal(`{
-  "error": "Bad Request: error converting followers_only.can_reply.always: policyURI public is not feasible for visibility followers_only"
+  "error": "Bad Request: error converting private.can_reply.always: policyURI public is not feasible for visibility private"
 }`, out)
 }