Fix broken URL

[sam-zilliqa]

The download url for the macOS version is correct in the master branch of this repo, but seems the prod site is not running this version, as the url there is wrong.

bad URL used in prod:
https://github.com/Zilliqa/ceres/releases/latest/download/Ceres-0.2.5.dmg
from:
https://dev.zilliqa.com/docs/dev/dev-tools-ceres#download-ceres

Correct URL used in master branch:
https://github.com/Zilliqa/ceres/releases/download/v0.2.5/Ceres-0.2.5.dmg
from:
https://github.com/Zilliqa/dev-portal/blob/master/docs/dev/dev-tools-ceres.mdx#download-ceres