address review comments

Author: laurit

instrumentation/spring/spring-boot-autoconfigure/src/main/java/io/opentelemetry/instrumentation/spring/autoconfigure/internal/instrumentation/logging/LogbackAppenderInstaller.java

@@ -172,7 +172,7 @@ private static void addMdcAppender(
     initializeMdcAppenderFromProperties(applicationEnvironmentPreparedEvent, openTelemetryAppender);
     openTelemetryAppender.start();
     logger.addAppender(openTelemetryAppender);
-    // move existing appenders under otel mdc appender
+    // move existing appenders under otel mdc appender, so they could observe the added mdc values
     for (Iterator<Appender<ILoggingEvent>> i = logger.iteratorForAppenders(); i.hasNext(); ) {
       Appender<ILoggingEvent> appender = i.next();
       if (appender != openTelemetryAppender) {

instrumentation/spring/spring-boot-autoconfigure/src/testLogbackAppender/java/io/opentelemetry/instrumentation/spring/autoconfigure/internal/instrumentation/logging/CustomListAppender.java

@@ -8,10 +8,7 @@
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.read.ListAppender;
 
-/**
- * This class is internal and is hence not for public use. Its APIs are unstable and can change at
- * any time.
- */
+@SuppressWarnings("OtelInternalJavadoc")
 public class CustomListAppender extends ListAppender<ILoggingEvent> {
   public static boolean lastLogHadTraceId;