Replace deprecated defaultSourceSetName with defaultSourceSet.name

Author: Abduqodiri Qurbonzoda

plugin/main/src/kotlinx/benchmark/gradle/BenchmarksExtension.kt

@@ -53,7 +53,7 @@ open class BenchmarksExtension(val project: Project) {
                     val target = multiplatform.targets.findByName(name)
                     // We allow the name to be either a target or a source set
                     when (val compilation = target?.compilations?.findByName(KotlinCompilation.MAIN_COMPILATION_NAME)
-                        ?: multiplatform.targets.flatMap { it.compilations }.find { it.defaultSourceSetName == name }) {
+                        ?: multiplatform.targets.flatMap { it.compilations }.find { it.defaultSourceSet.name == name }) {
                         null -> {
                             project.logger.warn("Warning: Cannot find a benchmark compilation '$name', ignoring.")
                             BenchmarkTarget(this, name) // ignore