[chore][exporter/logzioexporter] Enable goleak check (#31151)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
This enables `goleak` checks in the Logz.io exporter to help ensure no
goroutines are being leaked. This is a test only change as the only
thing necessary was to add a missing close call on a server in a test.

**Link to tracking Issue:** <Issue number if applicable>
#30438

**Testing:** <Describe what testing was performed and which tests were
added.>
All existing tests are passing, as well as added `goleak` check.

exporter/logzioexporter/go.mod

@@ -20,6 +20,7 @@ require (
 	go.opentelemetry.io/collector/semconv v0.95.0
 	go.opentelemetry.io/otel/metric v1.23.1
 	go.opentelemetry.io/otel/trace v1.23.1
+	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.27.0
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20240108191215-35c7eff3a6b1
 	google.golang.org/protobuf v1.32.0

exporter/logzioexporter/jsonlog_test.go

@@ -81,6 +81,7 @@ func TestSetTimeStamp(t *testing.T) {
 		recordedRequests, _ = io.ReadAll(req.Body)
 		rw.WriteHeader(http.StatusOK)
 	}))
+	defer func() { server.Close() }()
 	ld := generateLogsOneEmptyTimestamp()
 	cfg := &Config{
 		Region: "us",

exporter/logzioexporter/package_test.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package logzioexporter
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}