Prevent empty declaration of `@ConcurrencyLimit`

[sbrannen]

Overview

As a follow-up to #35461 and a comment left on the Spring Blog, we have decided to prevent empty declarations of @ConcurrencyLimit, thereby requiring users to explicitly declare the value for the limit.

Related Issues

• Introduce placeholder resolution support in @ConcurrencyLimit #35461
• Introduce placeholder resolution support in @ConcurrencyLimit #35470