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.

libraries/stdlib/js-v1/build.gradle

@@ -134,7 +134,6 @@ compileKotlin2Js {
             "-opt-in=kotlin.RequiresOptIn",
             "-opt-in=kotlin.ExperimentalMultiplatform",
             "-opt-in=kotlin.contracts.ExperimentalContracts",
-            "-XXLanguage:+RangeUntilOperator",
             "-Xforce-deprecated-legacy-compiler-usage"
         ]
     }
@@ -148,7 +147,6 @@ compileTestKotlin2Js {
             "-opt-in=kotlin.ExperimentalUnsignedTypes",
             "-opt-in=kotlin.ExperimentalStdlibApi",
             "-opt-in=kotlin.io.encoding.ExperimentalEncodingApi",
-            "-XXLanguage:+RangeUntilOperator",
         ]
     }
 }