Refactor integration test DecodeJSON calls to use generic return value (#37432)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: wxiaoguang <2114189+wxiaoguang@users.noreply.github.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/attachment_test.go

@@ -60,8 +60,7 @@ func testCreateAttachment(t *testing.T, session *TestSession, repoURL, issueOrRe
 	if expectedStatus != http.StatusOK {
 		return ""
 	}
-	var obj map[string]string
-	DecodeJSON(t, resp, &obj)
+	obj := DecodeJSON(t, resp, map[string]string{})
 	return obj["uuid"]
 }