[K/JS] Remove an internal system property and replace it with the new compiler flag

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/AbstractIncrementalJsCompilerRunnerTest.kt

@@ -43,9 +43,7 @@ abstract class AbstractIncrementalJsCompilerRunnerTest : AbstractIncrementalComp
             outputFile = File(destinationDir, "${testDir.name}.js").path
             sourceMap = true
             metaInfo = true
-            useDeprecatedLegacyCompiler = true
-            // TODO: It will be deleted after all of our internal vendors will use the new Kotlin/JS compiler
-            CompilerSystemProperties.KOTLIN_JS_COMPILER_LEGACY_FORCE_ENABLED.value = "true"
+            forceDeprecatedLegacyCompilerUsage = true
         }
 
     protected open val scopeExpansionMode = CompileScopeExpansionMode.NEVER

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/AbstractIncrementalMultiModuleJsCompilerRunnerTest.kt

@@ -29,9 +29,7 @@ abstract class AbstractIncrementalMultiModuleJsCompilerRunnerTest :
         K2JSCompilerArguments().apply {
             sourceMap = true
             metaInfo = true
-            useDeprecatedLegacyCompiler = true
-            // TODO: It will be deleted after all of our internal vendors will use the new Kotlin/JS compiler
-            CompilerSystemProperties.KOTLIN_JS_COMPILER_LEGACY_FORCE_ENABLED.value = "true"
+            forceDeprecatedLegacyCompilerUsage = true
         }
 
     override fun makeForSingleModule(