Adds dash to release version in release script

[duncanpharvey]

What does this PR do?

Adds a dash character - to the release version in the launch script so future release tags are consistent with previous versions.

Motivation

Release tag was created with a different pattern than that of previous versions

• https://github.com/DataDog/datadog-cloudformation-macro/tree/serverless-macro0.10.0
• https://github.com/DataDog/datadog-cloudformation-macro/tree/serverless-macro-0.9.0

Testing Guidelines

Additional Notes

Types of changes

• [x] Bug fix
• [ ] New feature
• [ ] Breaking change
• [ ] Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• [x] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [ ] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog