[chore][exporter/datadog] Re-enable TestTraceExporter (open-telemetry…

…#28827)

Re-enable TestTraceExporter.

Fixes
open-telemetry#27630

Co-authored-by: Pablo Baeyens <pbaeyens31+github@gmail.com>

exporter/datadogexporter/traces_exporter_test.go

@@ -229,7 +229,6 @@ func TestTracesSource(t *testing.T) {
 }
 
 func TestTraceExporter(t *testing.T) {
-	t.Skip("Flaky test on CI, see https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/27630")
 	metricsServer := testutil.DatadogServerMock()
 	defer metricsServer.Close()
 
@@ -259,6 +258,7 @@ func TestTraceExporter(t *testing.T) {
 			},
 			IgnoreResources: []string{},
 			flushInterval:   0.1,
+			TraceBuffer:     2,
 		},
 	}