[Gradle, JS] Set only one attribute for ir target

- Because if new library version can be consumed from old plugin, which doesn't know about new attribute
We don't add attribute for legacy variant, and Gradle find necessary variant with less attribute count

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinTargetConfigurator.kt

@@ -30,7 +30,6 @@ import org.jetbrains.kotlin.gradle.dsl.kotlinExtension
 import org.jetbrains.kotlin.gradle.plugin.mpp.*
 import org.jetbrains.kotlin.gradle.targets.js.KotlinJsTarget
 import org.jetbrains.kotlin.gradle.targets.js.KotlinJsTarget.Companion.IR
-import org.jetbrains.kotlin.gradle.targets.js.KotlinJsTarget.Companion.LEGACY
 import org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrTarget
 import org.jetbrains.kotlin.gradle.utils.lowerCamelCaseName
 import java.util.concurrent.Callable
@@ -449,10 +448,6 @@ internal fun Project.usageByName(usageName: String): Usage =
 fun Configuration.usesPlatformOf(target: KotlinTarget): Configuration {
     attributes.attribute(KotlinPlatformType.attribute, target.platformType)
 
-    if (target is KotlinJsTarget) {
-        attributes.attribute(KotlinJsTarget.jsModeAttribute, LEGACY)
-    }
-
     if (target is KotlinJsIrTarget) {
         attributes.attribute(KotlinJsTarget.jsModeAttribute, IR)
     }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/js/KotlinJsTarget.kt

@@ -155,7 +155,6 @@ constructor(
             String::class.java
         )
 
-        const val LEGACY = "legacy"
         const val IR = "ir"
 
         fun setupAttributesMatchingStrategy(attributesSchema: AttributesSchema) {