Build: remove explicit enabling of RangeUntilOperator

This feature is enabled by default since 1.8. Using the `-XXLanguage`
compiler argument leads to big warnings which are distracting during the
build.

kotlin-native/runtime/build.gradle.kts

@@ -546,7 +546,6 @@ konanArtifacts {
                 "-opt-in=kotlin.contracts.ExperimentalContracts",
                 "-opt-in=kotlin.ExperimentalMultiplatform",
                 "-opt-in=kotlin.native.internal.InternalForKotlinNative",
-                "-XXLanguage:+RangeUntilOperator",
         )
 
         commonStdlibSrcDirs.forEach { commonSrcDir(it) }