Use UnsynchronizedAppenderBase as base class for our logback appender
MODIFY
instrumentation/logback/logback-appender-1.0/library/src/main/java/io/opentelemetry/instrumentation/logback/appender/v1_0/OpenTelemetryAppender.java
instrumentation/logback/logback-appender-1.0/library/src/main/java/io/opentelemetry/instrumentation/logback/appender/v1_0/OpenTelemetryAppender.java
package io.opentelemetry.instrumentation.logback.appender.v1_0;
import ch.qos.logback.classic.spi.ILoggingEvent;
-import ch.qos.logback.core.AppenderBase;
+import ch.qos.logback.core.UnsynchronizedAppenderBase;
import io.opentelemetry.instrumentation.api.appender.internal.LogEmitterProvider;
import io.opentelemetry.instrumentation.api.appender.internal.LogEmitterProviderHolder;
import io.opentelemetry.instrumentation.logback.appender.v1_0.internal.LoggingEventMapper;
import io.opentelemetry.instrumentation.sdk.appender.internal.DelegatingLogEmitterProvider;
import io.opentelemetry.sdk.logs.SdkLogEmitterProvider;
-public class OpenTelemetryAppender extends AppenderBase<ILoggingEvent> {
+public class OpenTelemetryAppender extends UnsynchronizedAppenderBase<ILoggingEvent> {
private static final LogEmitterProviderHolder logEmitterProviderHolder =
new LogEmitterProviderHolder();

Use UnsynchronizedAppenderBase as base class for our logback appender (#5818)