Fix pool shrink

[minggo]

Re: #

Changelog

• fix the logic bug imported by https://github.com/cocos/cocos-engine/pull/16840

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Continuous Integration

This pull request:

• [ ] needs automatic test cases check.

  Manual trigger with @cocos-robot run test cases afterward.

• [ ] does not change any runtime related code or build configuration

  If any reviewer thinks the CI checks are needed, please uncheck this option, then close and reopen the issue.

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Compatibility Check

This pull request:

• [ ] changes public API, and have ensured backward compatibility with deprecated features.
• [ ] affects platform compatibility, e.g. system version, browser version, platform sdk version, platform toolchain, language version, hardware compatibility etc.
• [ ] affects file structure of the build package or build configuration which requires user project upgrade.
• [ ] introduces breaking changes, please list all changes, affected features and the scope of violation.

[github-actions[bot]]

Interface Check Report

! WARNING this pull request has changed these public interfaces:

@@ -19623,9 +19623,9 @@
         export class frustum extends Frustum {
             constructor();
         }
     }
-    export const VERSION = "3.8.4";
+    export const VERSION = "3.8.5";
     /**
      * @en
      * The main namespace of Cocos engine, all engine core classes, functions, properties and constants are defined in this namespace.
      * @zh