fix: remove invalid supports_prompt_caching parameter

Removed supports_prompt_caching parameter that was causing 400 errors.
Prompt caching is automatically enabled by Anthropic when the client
sends cache_control blocks in messages - no config needed.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

ai/litellm-config.yaml

@@ -4,35 +4,30 @@ model_list:
       model: anthropic/claude-sonnet-4-20250514
       api_key: os.environ/ANTHROPIC_API_KEY
       drop_params: true
-      supports_prompt_caching: true
 
   - model_name: claude-sonnet-4.5
     litellm_params:
       model: anthropic/claude-sonnet-4-5-20250929
       api_key: os.environ/ANTHROPIC_API_KEY
       drop_params: true
-      supports_prompt_caching: true
 
   - model_name: claude-3-5-sonnet
     litellm_params:
       model: anthropic/claude-3-5-sonnet-20241022
       api_key: os.environ/ANTHROPIC_API_KEY
       drop_params: true
-      supports_prompt_caching: true
 
   - model_name: claude-3-opus
     litellm_params:
       model: anthropic/claude-3-opus-20240229
       api_key: os.environ/ANTHROPIC_API_KEY
       drop_params: true
-      supports_prompt_caching: true
 
   - model_name: claude-3-haiku
     litellm_params:
       model: anthropic/claude-3-haiku-20240307
       api_key: os.environ/ANTHROPIC_API_KEY
       drop_params: true
-      supports_prompt_caching: true
 
 litellm_settings:
   drop_params: true