Upgrade to Logback 1.4.6

This commit includes a change to stop using an API in Logback that
has been deprecated without replacement. As Logback now only supports
.xml configuration files, it would only ever have thrown an
exception. The call to the API has been replaced with thrown an
exception directly.

Closes gh-34686

spring-boot-project/spring-boot-dependencies/build.gradle

@@ -783,7 +783,7 @@ bom {
 			]
 		}
 	}
-	library("Logback", "1.4.5") {
+	library("Logback", "1.4.6") {
 		group("ch.qos.logback") {
 			modules = [
 				"logback-access",

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/logback/LogbackLoggingSystem.java

@@ -33,7 +33,6 @@ import ch.qos.logback.classic.LoggerContext;
 import ch.qos.logback.classic.joran.JoranConfigurator;
 import ch.qos.logback.classic.jul.LevelChangePropagator;
 import ch.qos.logback.classic.turbo.TurboFilter;
-import ch.qos.logback.classic.util.ContextInitializer;
 import ch.qos.logback.core.joran.spi.JoranException;
 import ch.qos.logback.core.spi.FilterReply;
 import ch.qos.logback.core.status.OnConsoleStatusListener;
@@ -272,13 +271,13 @@ public class LogbackLoggingSystem extends AbstractLoggingSystem implements BeanF
 
 	private void configureByResourceUrl(LoggingInitializationContext initializationContext, LoggerContext loggerContext,
 			URL url) throws JoranException {
-		if (url.toString().endsWith("xml")) {
+		if (url.toString().endsWith(".xml")) {
 			JoranConfigurator configurator = new SpringBootJoranConfigurator(initializationContext, this.configurators);
 			configurator.setContext(loggerContext);
 			configurator.doConfigure(url);
 		}
 		else {
-			new ContextInitializer(loggerContext).configureByResource(url);
+			throw new IllegalArgumentException("Unsupported file extension in '" + url + "'. Only .xml is supported");
 		}
 	}