## Which issue(s) this PR fixes
Fixes this issue we started seeing popping up because of a change
introduced in #3496:
```python3
File "/etc/app/apps/metrics_exporter/views.py", line 22, in get
result = generate_latest(application_metrics_registry).decode("utf-8")
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/site-packages/prometheus_client/exposition.py", line 198, in generate_latest
for metric in registry.collect():
File "/usr/local/lib/python3.11/site-packages/prometheus_client/registry.py", line 97, in collect
yield from collector.collect()
File "/etc/app/apps/metrics_exporter/metrics_collectors.py", line 56, in collect
alert_groups_total, missing_org_ids_1 = self._get_alert_groups_total_metric(org_ids)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/etc/app/apps/metrics_exporter/metrics_collectors.py", line 97, in _get_alert_groups_total_metric
org_id_from_key = RE_ALERT_GROUPS_TOTAL.match(org_key).groups()[0]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'groups'
```
```python3
>>> import re
>>> ALERT_GROUPS_TOTAL = "oncall_alert_groups_total"
>>> _RE_BASE_PATTERN = r"{{?{}}}?_(\d+)"
>>> RE_ALERT_GROUPS_TOTAL = re.compile(_RE_BASE_PATTERN.format(ALERT_GROUPS_TOTAL))
>>> org_key = "{oncall_alert_groups_total}_1"
>>> RE_ALERT_GROUPS_TOTAL.match(org_key).groups()[0]
'1'
>>> org_key = "oncall_alert_groups_total_1"
>>> RE_ALERT_GROUPS_TOTAL.match(org_key).groups()[0]
'1'
```
## Checklist
- [x] Unit, integration, and e2e (if applicable) tests updated
- [ ] Documentation added (or `pr:no public docs` PR label added if not
required)
- [ ] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)
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