revert changes in SpanTracer

Author: blakeli0

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/SpanTracer.java

@@ -85,15 +85,6 @@ public SpanTracer(Tracer tracer, ApiTracerContext apiTracerContext) {
     buildAttributes();
   }
 
-  @Override
-  public Scope inScope() {
-    if (attemptSpan == null) {
-      return () -> {};
-    }
-    final io.opentelemetry.context.Scope otelScope = attemptSpan.makeCurrent();
-    return () -> otelScope.close();
-  }
-
   private static String resolveAttemptSpanName(ApiTracerContext apiTracerContext) {
     if (apiTracerContext.transport() == ApiTracerContext.Transport.GRPC) {
       // gRPC Uses the full method name as span name.