docs: remove remaining Chinese documentation files

Removed:
- 流式工具调用问题深度分析.md
- 流式工具调用问题详解（图文版）.md

All documentation is now in English following Spring project standards.

Signed-off-by: Spring AI Contributor <contributor@example.com>
Signed-off-by: shaojie <741047428@qq.com>

Author: JGoP-L