use react router link instead of a tag for about link

[licaroline]

Description

On staging, the link for About GoVoteGSO & CodeForGSO sends you to https://staging.govotegso.org/about or https://staging.govotegso.org/about#/. I can't replicate the bug locally, but I believe it's because we're using <a> instead of <Link>.

Related Issue

https://github.com/codeforgso/GoVote/issues/206

How Has This Been Tested?

Tested locally

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.