Underscore Prepended to Numeric Column Labels

#### Environment details

- OS type and version: MacOS Sonoma 4.5 (23F79)
- Python version: `3.11.6`
- pip version: `23.3.1
- `sqlalchemy-bigquery` version: `1.11.0`

#### Steps to reproduce

1. Attempt to label a column with a numeric column name (with or without quoted_name)
2. Get the cursor description for this column. The name has a prepended underscore

#### Code example

```python
import sqlalchemy as sa
engine = ****insert engine creation here****

with engine.connect() as conn:
a = sa.literal("a")
labeled_col = a.label(sa.sql.quoted_name("2", quote=True))
res = conn.execute(sa.select(labeled_col))
name = res.cursor.description[0].name

res_2 = conn.execute("SELECT 'a' AS `2`")
name_2 = res_2.cursor.description[0].name

assert name == name_2 == "2"
```

#### Stack trace
```
AssertionError: assert '_2' == '2'
```