Remove wrong usage of commons-lang3

Closes gh-11267

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/assertj/AssertProviderApplicationContextInvocationHandler.java

@@ -24,9 +24,8 @@ import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.function.Supplier;
 
-import org.apache.commons.lang3.builder.ToStringBuilder;
-
 import org.springframework.context.ApplicationContext;
+import org.springframework.core.style.ToStringCreator;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -98,7 +97,7 @@ class AssertProviderApplicationContextInvocationHandler implements InvocationHan
 					+ this.applicationContextType.getName() + "[startupFailure="
 					+ this.startupFailure.getClass().getName() + "]";
 		}
-		ToStringBuilder builder = new ToStringBuilder(this.applicationContext)
+		ToStringCreator builder = new ToStringCreator(this.applicationContext)
 				.append("id", this.applicationContext.getId())
 				.append("applicationName", this.applicationContext.getApplicationName())
 				.append("beanDefinitionCount",

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/assertj/ApplicationContextAssertProviderTests.java

@@ -197,8 +197,8 @@ public class ApplicationContextAssertProviderTests {
 				this.mockContextSupplier);
 		assertThat(context.toString())
 				.startsWith(
-						"Started application org.springframework.context.ConfigurableApplicationContext$MockitoMock")
-				.endsWith("[id=<null>,applicationName=<null>,beanDefinitionCount=0]");
+						"Started application [ConfigurableApplicationContext.MockitoMock")
+				.endsWith("id = [null], applicationName = [null], beanDefinitionCount = 0]");
 	}
 
 	@Test