fix: wrong default branch checkout from release-0.10 to release-0.12 in install script

[Himess]

Currently, the install script defaults to checking out the release-0.10 branch when updating or pulling the repository. However, the latest stable version is release-0.12. This causes outdated configuration files (like broker.toml and compose.yml) to be pulled, which affects performance and causes inconsistencies with the latest documentation.