Disable fork for deployments.

[mshima]

Problem: when executing jdl with a custom blueprint option (from app generator) like jhipster jdl microservice.jdl --blueprints kotlin --skip-ktlint-format, jdl command with fork serializes options back to cli options and executes deployments generators using cli with every option (eg: jhipster docker-compose --blueprints kotlin --skip-ktlint-format), causing an unknown option error.

Fork is supposed to run multiples generators in parallel making it faster, but deployments are small and will not have a big impact on the execution time.

Drop fork support for deployments, preventing the unknown option error.

Closes #14870.

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