Clear system property set by log file registration

Closes gh-20790

Author: wilkinsona

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/logging/LoggingApplicationListenerIntegrationTests.java

@@ -30,6 +30,7 @@
 import org.springframework.boot.context.event.ApplicationStartingEvent;
 import org.springframework.boot.logging.LogFile;
 import org.springframework.boot.logging.LoggingSystem;
+import org.springframework.boot.logging.LoggingSystemProperties;
 import org.springframework.boot.testsupport.system.CapturedOutput;
 import org.springframework.boot.testsupport.system.OutputCaptureExtension;
 import org.springframework.context.ApplicationListener;
@@ -64,6 +65,9 @@ void logFileRegisteredInTheContextWhenApplicable(@TempDir File tempDir) throws E
 			assertThat(service.logFile).isNotNull();
 			assertThat(service.logFile.toString()).isEqualTo(logFile);
 		}
+		finally {
+			System.clearProperty(LoggingSystemProperties.LOG_FILE);
+		}
 	}
 
 	@Test