Update to Erlang 29.0.3.

[conradwt]

This PR supports the following features:

• update to Erlang 29.0.3

[github-actions]

Docker image tag(s) pushed:

ghcr.io/conradwt/zero-to-graphql-using-elixir:gha-28714053261
ghcr.io/conradwt/zero-to-graphql-using-elixir:pr-318 

Labels added to images:

org.opencontainers.image.created=2026-07-04T17:31:05.255Z
org.opencontainers.image.description=The purpose of this example is to provide details as to how one would go about using GraphQL with the Elixir Language.
org.opencontainers.image.licenses=MIT
org.opencontainers.image.revision=053de03003602f2b91b24d66c1b31699c221ef2d
org.opencontainers.image.source=https://github.com/conradwt/zero-to-graphql-using-elixir
org.opencontainers.image.title=zero-to-graphql-using-elixir
org.opencontainers.image.url=https://github.com/conradwt/zero-to-graphql-using-elixir
org.opencontainers.image.version=gha-28714053261