Update extensions.json: Anthropic.claude-code is not malware

[kineticsquid]

anthropics/claude-code#5762

• I have read the note above about PRs contributing or fixing extensions
• I have tried reaching out to the extension maintainers about publishing this extension to Open VSX (if not, please create an issue in the extension's repo using this template).
• This extension has an OSI-approved OSS license (we don't accept proprietary extensions in this repository)

Description

Have confirmed with the Anthropic team that this is not malware.