[codex] remove duplicate Open Source Diversity card

[Sean-Kenneth-Doherty]

Summary

• remove the second identical Open Source Diversity project card
• keep the earlier Open Source Diversity entry with the same live contributor link, avatar, description, and tags
• reduce duplicate cards in the project list UI

Validation

• Open Source Diversity source count is 1 via src/data/projects.js import
• git diff --check
• GITHUB_TOKEN=$(gh auth token) pnpm build
• generated dist/index.html Open Source Diversity count is 1 before restoring generated files
• contributor link and avatar both return HTTP 200

Related to #501

[Sean-Kenneth-Doherty]

Validated locally on head a7b8d17b63c0a57f072c3b12b1a7eb9589edbb05 in an isolated worktree:

• imported src/data/projects.js and confirmed Open Source Diversity source count is 1
• kept card link https://github.com/opensourcediversity/opensourcediversity.org/contribute returns HTTP 200
• kept avatar https://avatars1.githubusercontent.com/u/31018274?s=200&v=4 returns HTTP 200
• git diff --check origin/main...HEAD && git diff --check
• GITHUB_TOKEN=$(gh auth token) pnpm build
• checked generated dist/index.html before restoring generated files; Open Source Diversity appears once

All passed. gh pr checks reports no hosted checks on this branch.