fix(fct_transit_data_quality_issues): removes duplicate issues create…

[vevetron]

…d due to unnesting by only selecting first dataset

Description

Previously the codebase unnested when multiple gtfs datasets (and services) were listed in an issue. Which could make sure we don't lose any information, but really just capturing the first gtfs dataset is sufficient.

Resolves #3407

Type of change

• Bug fix (non-breaking change which fixes an issue)

How has this been tested?

poetry run dbt run -s  +calitp_warehouse.mart.transit_database.fct_transit_data_quality_issues --full-refresh
then
SELECT count(*) FROM `cal-itp-data-infra-staging.vb_mart_transit_database.fct_transit_data_quality_issues` order by 

```-> Produced 284 issues up to issue 300, which is accurate at a snapshot of the airtable issue table
## Post-merge follow-ups

- [x] No action required

[github-actions]

Warehouse report 📦

DAG

Legend (in order of precedence)

Resource type	Indicator	Resolution
Large table-materialized model	Orange	Make the model incremental
Large model without partitioning or clustering	Orange	Add partitioning and/or clustering
View with more than one child	Yellow	Materialize as a table or incremental
Incremental	Light green
Table	Green
View	White