docs: fix AEP paper link

[tharune]

Summary

• update AEP-5’s economics paper link from the nonexistent AEP-2 PDF path to the existing AEP-5 PDF
• fix a typo in the same sentence (publised -> published)

Verification

• curl -L -I https://github.com/akash-network/AEP/blob/main/spec/aep-2/economics.pdf returns 404
• curl -L -I https://github.com/akash-network/AEP/blob/main/spec/aep-5/economics.pdf returns 200
• confirmed the local AEP-5 PDF exists at src/content/aeps/aep-5/economics.pdf
• git diff --check

[tharune]

Closing this wrong-repo AEP mirror PR per maintainer guidance. This fix is already recreated against the source AEP repo here: akash-network/AEP#106