CI - install synplify/monorepo-builder globally

[adamziel]

This pull request updates how the symplify/monorepo-builder dependency is managed and used in the Composer release workflow. The main change is moving monorepo-builder from a project dependency to a global Composer dependency, and updating the workflow to use the globally installed binary.

Dependency management:

• Removed symplify/monorepo-builder from composer.json project require-dev dependencies, so it is no longer installed with project dependencies.
• Added a step to the GitHub Actions workflow to install monorepo-builder globally using Composer before running release commands.

Workflow execution:

• Updated the workflow to invoke the globally installed monorepo-builder binary using Composer's global bin directory, instead of the local vendor/bin path.