log/logtest: Remove RecordFactory (#6492)

Fixes #6485

Towards #6341

`RecordFactory` is unused.

Author: pellared

CHANGELOG.md

@@ -12,6 +12,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Drop support for [Go 1.22]. (#6381, #6418)
 - Remove `Resource` field from `EnabledParameters` in `go.opentelemetry.io/otel/sdk/log`. (#6494)
+- Remove `RecordFactory` type from  `go.opentelemetry.io/otel/log/logtest`. (#6492)
 
 ### Changed