Update version of the grafana fork of postgres_exporter to include
a fix for a panic with Cloud Sql Postgres in pg_settings collector.

The fix is included in upstream postgres_exporter v0.19.0, which will
be shipped with Alloy 1.14.0. This backport is targeted for Alloy 1.13.

Fork patch: grafana/postgres_exporter#30

Fixes #5502

…k to fix pg_settings (#5574)

### Brief description of Pull Request
Update version of the grafana fork of postgres_exporter to include a fix
for a panic with Cloud Sql Postgres in pg_settings collector.

### Pull Request Details
The upstream fix is included in upstream postgres_exporter v0.19.0,
which will be shipped with Alloy 1.14.0. This backport is targeted for
Alloy 1.13.

Fork patch: grafana/postgres_exporter#30

### Issue(s) fixed by this Pull Request
Fixes #5502

### Notes to the Reviewer

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### PR Checklist

<!-- Remove items that do not apply. For completed items, change [ ] to
[x]. -->

- [ ] Documentation added
- [ ] Tests updated
- [ ] Config converters updated