chore(deps): bump com.openai:openai-java from 4.78.0 to 4.81.0

Bumps [com.openai:openai-java](https://github.com/openai/openai-java) from 4.78.0 to 4.81.0.
- [Release notes](https://github.com/openai/openai-java/releases)
- [Changelog](https://github.com/openai/openai-java/blob/main/CHANGELOG.md)
- [Commits](openai/openai-java@v4.78.0...v4.81.0)

---
updated-dependencies:
- dependency-name: com.openai:openai-java
  dependency-version: 4.81.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

agentscope-dependencies-bom/pom.xml

@@ -78,7 +78,7 @@
         <google-genai.version>1.78.0</google-genai.version>
         <dashscope-sdk-java.version>2.23.2</dashscope-sdk-java.version>
         <bailian.version>2.14.4</bailian.version>
-        <openai-java.version>4.78.0</openai-java.version>
+        <openai-java.version>4.81.0</openai-java.version>
         <anthropic.version>2.72.0</anthropic.version>
         <mcp.version>0.17.2</mcp.version>
         <slf4j.version>2.0.17</slf4j.version>