Docs：remove repeated word

[MarkShen1992]

remove repeated word in i18n/zh/docusaurus-plugin-content-docs/current/getting-started/introduction.md

Description of your changes

I have:

• [x] Read and followed KubeVela's contribution process.
• [ ] Update sidebar.js if adding a new page.
• [x] Run yarn start to ensure the changes has taken effect.

Special notes for your reviewer