"TextureImporterFormat.AutomaticTruecolor" is marked as obsolete starting from 2023.2. This is intended, it has been marked as deprecated since Unity 5.5.
In order to upgrade the problematic code, please refer to the deprecation notes. (also see: "TextureImporterFormat.Automatic")
We recommend making use of preprocessor directives (for example: #if UNITY_5_5_OR_NEWER) in order to run different (updated) code on newer versions.