The LiteLLM-based LLM.call() (used by Groq, OpenAI-compatible, etc.)
does not go through BaseLLM._format_messages() which strips the
cache_breakpoint flag. This causes providers like Groq to reject
messages with 'cache_breakpoint' as an unsupported property.
Strip the flag in _prepare_completion_params() so it is removed from
the wire payload for all providers using the LiteLLM code path.
Fixes#5886
Co-Authored-By: João <joao@crewai.com>
