fix the issue of linking 'Learn more' button to handbook (#1606)

[ChamodP]

Purpose

The purpose of this PR is to fix # not get linked to the handbook when click the 'Learn more' btn on join our team page

Goals

Approach

changed the href to the handbook URL

Screenshots

Preview Link

https://pr-{PR_NUMBER}-sef-site.surge.sh/

Checklist

• [x] I have read and understood the development best practices guidelines
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas

Related PRs

## Learning

[YoshithaRathnayake]

Thank you @ChamodP, Good job!

@kumuditha-udayanga couldn't tell him to add a target="_blank" 😢 I'll create another issue for that then

[kumuditha-udayanga]

Hi @YoshithaRathnayake, Yeah it's good to have