Enhance KnowledgeConfig with field descriptions

- Updated `results_limit` and `score_threshold` in `KnowledgeConfig` to use Pydantic's `Field` for improved documentation and clarity.
- Added descriptions to both parameters to provide better context for their usage in knowledge retrieval configuration.

src/crewai/knowledge/knowledge_config.py

@@ -1,6 +1,9 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 
 
 class KnowledgeConfig(BaseModel):
-    results_limit: int = 3
-    score_threshold: float = 0.35
+    results_limit: int = Field(default=3, description="The number of results to return")
+    score_threshold: float = Field(
+        default=0.35,
+        description="The minimum score for a result to be considered relevant",
+    )