refactor: comment hidden default is false (#2482)

#### What type of PR is this?
/kind improvement
/area core
/milestone 2.0

#### What this PR does / why we need it:
创建评论时 hidden 字段默认为 false
#### Which issue(s) this PR fixes:

Fixes #

#### Special notes for your reviewer:
/cc @halo-dev/sig-halo 
#### Does this PR introduce a user-facing change?

```release-note
None
```

src/main/java/run/halo/app/content/comment/CommentServiceImpl.java

@@ -81,7 +81,7 @@ public class CommentServiceImpl implements CommentService {
                 }
                 comment.getSpec()
                     .setApproved(Boolean.FALSE.equals(commentSetting.getRequireReviewForNew()));
-                comment.getSpec().setHidden(!comment.getSpec().getApproved());
+                comment.getSpec().setHidden(false);
                 if (comment.getSpec().getOwner() != null) {
                     return Mono.just(comment);
                 }

src/test/java/run/halo/app/content/comment/CommentServiceImplTest.java

@@ -141,7 +141,7 @@ class CommentServiceImplTest {
                         "top": false,
                         "allowNotification": true,
                         "approved": false,
-                        "hidden": true,
+                        "hidden": false,
                         "subjectRef": {
                             "group": "content.halo.run",
                             "version": "v1alpha1",