Remove workaround for flow

[acktsap]

spring-projects/spring-batch#4092 is fixed

spring-batch-plus/spring-batch-plus-kotlin/src/main/kotlin/com/navercorp/spring/batch/plus/kotlin/configuration/ConcreteFlowBuilderDsl.kt

Lines 221 to 226 in ccd1200

	internal fun build(): T = this.flowBuilder.build().apply {
	// resolve https://github.com/spring-projects/spring-batch/issues/4092
	if (this is SimpleFlow) {
	afterPropertiesSet()
	}
	}

Since v5.1.0-m2, v5.0.3, v4.3.9