changelog: update changelog with v1.4.2 information

Merge pull request libgit2#6224 from libgit2/ethomson/v1.4.1

v1.4.1

Merge pull request libgit2#6214 from libgit2/ethomson/v1.4

libgit2 v1.4

OpenCOR: allow cloning in a non-empty directory.

v1.3: very very last-minute changelog updates

url: ensure minimum components for formatting

OpenCOR: allow cloning in a non-empty directory.