Prepare 1.5.6 release

[stnguyen90]

What does this PR do?

• Bump appwrite version to 1.5.6
• Add 1.5.6 changes to CHANGES.md

Test Plan

Automated tests should pass.

In addition, the following manual tests should be performed:

docker compose build
docker tag appwrite-dev appwrite/appwrite:1.5.6
docker run -it --rm \
    --volume /var/run/docker.sock:/var/run/docker.sock \
    --volume "$(pwd)"/appwrite:/usr/src/code/appwrite:rw \
    --entrypoint=install \
    appwrite/appwrite:1.5.6

Related PRs and Issues

None

Checklist

• Have you read the Contributing Guidelines on issues?
• If the PR includes a change to an API's metadata (desc, label, params, etc.), does it also include updated API specs and example docs?

[stnguyen90]

outdated and superseded by #8168