Remove ResourceUtils.getURL logging config check

Remove `ResourceUtils.getURL` checking from `LoggingApplicationListener`
so that logging systems can implement custom location support.

Prior to this commit, we checked in the listener if the specified config
location could be opened as a URL. This unfortunately prevents Log4J
extensions such as `log4j-spring-cloud-config-client` from implementing
configurable SSL and credentials support.

See gh-22946

Author: rgoers

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/logging/LoggingApplicationListener.java

@@ -53,7 +53,6 @@
 import org.springframework.core.log.LogMessage;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
-import org.springframework.util.ResourceUtils;
 import org.springframework.util.StringUtils;
 
 /**
@@ -314,7 +313,6 @@ private void initializeSystem(ConfigurableEnvironment environment, LoggingSystem
 		}
 		else {
 			try {
-				ResourceUtils.getURL(logConfig).openStream().close();
 				system.initialize(initializationContext, logConfig, logFile);
 			}
 			catch (Exception ex) {