integration: Delete Opbeat integration.

Opbeat was acquired by Elastic in 2017[1] and maintained until Elastic
APM went live[2]. Now that Elastic APM is online, it looks like Opbeat
repositories have been marked as archived/unmaintained[3].

[1]: https://www.elastic.co/blog/welcome-opbeat-to-the-elastic-family
[2]:
https://www.elastic.co/observability/application-performance-monitoring
[3]: https://github.com/opbeat

zerver/lib/integrations.py

@@ -444,13 +444,6 @@ WEBHOOK_INTEGRATIONS: list[WebhookIntegration] = [
     WebhookIntegration("mention", ["marketing"], display_name="Mention"),
     WebhookIntegration("netlify", ["continuous-integration", "deployment"], display_name="Netlify"),
     WebhookIntegration("newrelic", ["monitoring"], display_name="New Relic"),
-    WebhookIntegration(
-        "opbeat",
-        ["monitoring"],
-        display_name="Opbeat",
-        stream_name="opbeat",
-        function="zerver.webhooks.opbeat.view.api_opbeat_webhook",
-    ),
     WebhookIntegration("opencollective", ["communication"], display_name="Open Collective"),
     WebhookIntegration("opsgenie", ["meta-integration", "monitoring"]),
     WebhookIntegration("pagerduty", ["monitoring"], display_name="PagerDuty"),
@@ -785,7 +778,6 @@ DOC_SCREENSHOT_CONFIG: dict[str, list[BaseScreenshotConfig]] = {
         ScreenshotConfig("incident_acknowledged_new.json", "002.png"),
         ScreenshotConfig("incident_closed_new.json", "003.png"),
     ],
-    "opbeat": [ScreenshotConfig("error_reopen.json")],
     "opencollective": [ScreenshotConfig("one_time_donation.json")],
     "opsgenie": [ScreenshotConfig("addrecipient.json", image_name="000.png")],
     "pagerduty": [ScreenshotConfig("trigger_v2.json")],