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

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

Check all that apply

• 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