Add span kind assertions to OpenTelemetryTracingBackend tests

Co-authored-by: Adam Warski <adamw@users.noreply.github.com>

Author: github-actions[bot]

observability/opentelemetry-backend/src/test/scala/sttp/client4/opentelemetry/OpenTelemetryTracingBackendTest.scala

@@ -33,6 +33,7 @@ class OpenTelemetryTracingBackendTest extends AnyFlatSpec with Matchers {
     val span = spanItems.head
 
     span.getName() shouldBe "GET"
+    span.getKind() shouldBe io.opentelemetry.api.trace.SpanKind.CLIENT
 
     val attributes = span.getAttributes().asMap().asScala
     attributes(UrlAttributes.URL_FULL) shouldBe "http://test.com/foo"
@@ -58,6 +59,7 @@ class OpenTelemetryTracingBackendTest extends AnyFlatSpec with Matchers {
     spanItems should have size 1
 
     val span = spanItems.head
+    span.getKind() shouldBe io.opentelemetry.api.trace.SpanKind.CLIENT
     val attributes = span.getAttributes().asMap().asScala
     attributes(UrlAttributes.URL_FULL) shouldBe "http://test.com/foo"
     attributes(ErrorAttributes.ERROR_TYPE) shouldBe "RuntimeException"