Use latest swift-tracing commit

Author: slashmo

Sources/AsyncHTTPClient/HTTPClient.swift

@@ -390,7 +390,7 @@ public class HTTPClient {
                                                               eventLoop eventLoopPreference: EventLoopPreference,
                                                               context: LoggingBaggageContextCarrier,
                                                               deadline: NIODeadline? = nil) -> Task<Delegate.Response> {
-        var span = InstrumentationSystem.tracingInstrument.startSpan(named: request.method.rawValue, context: context, ofKind: .client, at: nil)
+        var span = InstrumentationSystem.tracingInstrument.startSpan(named: request.method.rawValue, context: context, ofKind: .client)
         span.attributes.http.method = request.method.rawValue
         span.attributes.http.scheme = request.scheme
         span.attributes.http.target = request.uri

Tests/AsyncHTTPClientTests/HTTPClientTests.swift

@@ -2715,16 +2715,18 @@ private final class TestTracer: TracingInstrument {
         named operationName: String,
         context: BaggageContextCarrier,
         ofKind kind: SpanKind,
-        at timestamp: Timestamp?
+        at timestamp: Timestamp
     ) -> Span {
         let span = TestSpan(operationName: operationName,
                             kind: kind,
-                            startTimestamp: timestamp ?? .now(),
+                            startTimestamp: timestamp,
                             context: context.baggage)
         recordedSpans.append(span)
         return span
     }
 
+    func forceFlush() {}
+
     func extract<Carrier, Extractor>(
         _ carrier: Carrier,
         into context: inout BaggageContext,