refactor(mem-reader): remove dead remove_prompt_example branch in StrategyStructMemReader

[nuthalapativarun]

Description

In StrategyStructMemReader._get_llm_response, the remove_prompt_example flag had no effect: the strategy prompt template does not contain SIMPLE_STRUCT_MEM_READER_EXAMPLE, so prompt.replace(examples, "") was always a no-op.

Removed the dead branch and the now-unused examples variable. The remove_prompt_example config field is preserved — it is still used correctly in SimpleStructMemReader and MultiModalStructMemReader.

Related Issue (Required): Fixes #1792

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (does not change functionality, e.g. code style improvements, linting)
• Documentation update

How Has This Been Tested?

• Unit Test

Checklist

• I have performed a self-review of my own code | 我已自行检查了自己的代码
• I have commented my code in hard-to-understand areas | 我已在难以理解的地方对代码进行了注释
• I have added tests that prove my fix is effective or that my feature works | 我已添加测试以证明我的修复有效或功能正常
• I have created related documentation issue/PR in MemOS-Docs (if applicable) | 我已在 MemOS-Docs 中创建了相关的文档 issue/PR（如果适用）
• I have linked the issue to this PR (if applicable) | 我已将 issue 链接到此 PR（如果适用）
• I have mentioned the person who will review this PR | 我已提及将审查此 PR 的人

[nuthalapativarun]

Hi maintainers, just a friendly bump on this one — it's been green and mergeable for about a week now. Let me know if anything else is needed for review. Thanks!

[Memtensor-AI]

Automated Test Results: PASSED

Cloud test-engine rerun against dev-v2.0.22 completed successfully.

• Run: tr-ef838e17-283 on cloud test-engine 10010
• memos_python_core/changed-python-source: 2 passed, 0 failed, 0 skipped

Manual code review is still required before merge.