[Hotfix] Update KNBS data links

[kilemensi]

Description

Update KNBS data links

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Screenshots

~https://www.knbs.or.ke/download/economic-survey-2018/~ https://www.knbs.or.ke/?wpdmpro=economic-survey-2018 ~https://www.knbs.or.ke/download/statistics-abstract-2018/~ https://www.knbs.or.ke/?wpdmpro=statistics-abstract-2018

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation