Fix broken links in the README.md file

Created by: chenejac

VIVO GitHub issue: 3905

What does this pull request do?

Fix broken links in the Vitro r readme file.

How should this be tested?

• Open https://github.com/vivo-project/Vitro/blob/main/README.md
• Click on the "VIVO" link and "VIVO community" link (at the bottom of README.md) file
• Pages should be opened