Design update to match new OKFN brand guidelines

[lucpretti]

This issue covers both the Project Repository and the Global Directory.

For both sites, we need to:

---

• Replace OKFN logo both in the header and footer

Assets for the above:

• OKFN full logo (SVG): https://drive.google.com/file/d/1Yao2GS38sR2laWH9VpmSv9j6zmyZcpOm/view?usp=sharing
• OKFN white logo (SVG): https://drive.google.com/file/d/1ZE8Zh0vGC78_cZG1jPP1z6q1DxA99rIz/view?usp=sharing

---

• Delete the sentence "Refer to our attributions page for attributions of other work on the site" from the footer, as there's no such page on the new website.