[Minor] fix duplicate/merge issue in Gravitino CLI model command (apa…

…che#6101)

### What changes were proposed in this pull request?

remove duplicate if statement.

### Why are the changes needed?

Looks like a merge issue.

Fix: # N/A

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

tested locally

clients/cli/src/main/java/org/apache/gravitino/cli/GravitinoCommandLine.java

@@ -139,8 +139,6 @@ private void executeCommand() {
       handleCatalogCommand();
     } else if (entity.equals(CommandEntities.METALAKE)) {
       handleMetalakeCommand();
-    } else if (entity.equals(CommandEntities.MODEL)) {
-      handleModelCommand();
     } else if (entity.equals(CommandEntities.TOPIC)) {
       handleTopicCommand();
     } else if (entity.equals(CommandEntities.FILESET)) {