[chore][receiver/gitproviderreceiver] Enable goleak check in GitHub s…

…craper (#32362)

**Description:** 
Enable `goleak` check in the `internal/scraper/githubscraper` package of
the Git Provider receiver to help ensure no goroutines are being leaked.
This is a test only change, a `Close` call was missing on a server in a
test.

**Link to tracking Issue:** #30438 

**Testing:**
All existing tests are passing, as well as added `goleak` check.

receiver/gitproviderreceiver/internal/scraper/githubscraper/helpers_test.go

@@ -649,6 +649,7 @@ func TestGetContributors(t *testing.T) {
 			ghs.cfg.GitHubOrg = tc.org
 
 			server := httptest.NewServer(tc.server)
+			defer func() { server.Close() }()
 
 			client := github.NewClient(nil)
 			url, _ := url.Parse(server.URL + "/api-v3" + "/")

receiver/gitproviderreceiver/internal/scraper/githubscraper/package_test.go

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