fix: ensure logger debug calls always return true

[gugaiz]

Issue #304

Description of changes

Modify logger debug behavior to return true regardless of the log level, ensuring dependent processes like state machines in solidus function correctly

Context

In Rails’ default logger, a call to logger.debug always returns true regardless of the log level, preserving compatibility with code that relies on the return value. However, rails_semantic_logger deviates from this behavior, returning false when the log level does not allow the message to be logged. This discrepancy can cause unexpected issues in frameworks like Solidus or other applications using state machines or similar logic.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[reidmorrison]

Unfortunately the ship has sailed on making a breaking change like this when Semantic Logger has behaved this way for over 10 years. We are very likely to break existing code for someone that looks at the return code.
If the return code has no meaning, then it should nil instead of true.