chore: remove incorrect index declaration (#6427)

#### What type of PR is this?
/milestone 2.19.x
/area core
/kind cleanup

#### What this PR does / why we need it:
删除对文章错误的索引声明

#### Does this PR introduce a user-facing change?
```release-note
None
```

application/src/main/java/run/halo/app/infra/SchemeInitializer.java

@@ -180,10 +180,6 @@ public class SchemeInitializer implements ApplicationListener<ApplicationContext
                     var contributors = post.getStatusOrDefault().getContributors();
                     return contributors == null ? Set.of() : Set.copyOf(contributors);
                 })));
-            indexSpecs.add(new IndexSpec()
-                .setName("status.categories")
-                .setIndexFunc(
-                    simpleAttribute(Post.class, post -> post.getStatusOrDefault().getExcerpt())));
             indexSpecs.add(new IndexSpec()
                 .setName("status.phase")
                 .setIndexFunc(