What is that thing and is it possible to get rid of it? I don't have kotlin scripts (only Gradle build script)

It is used by Gradle itself, so there shouldn't be any issues. Anything with that orangeish/yellow background (whatever you want to call that color) is on the Gradle classpath. That will include any scripts, and dependencies Gradle itself is pulling in, or any dependencies needed for any Gradle plugins you are using.