In scan_parquet(), include_file_paths returns twice the same column

[etiennebacher]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import polars as pl

# need to create the folders "data/b=1" and "data/b=2" first
pl.DataFrame({"a": [1]}).write_parquet("data/b=1/data.parquet")
pl.DataFrame({"a": [2]}).write_parquet("data/b=2/data.parquet")

pl.scan_parquet("data", include_file_paths="file_paths").collect()

Log output

shape: (2, 4)
┌─────┬─────┬───────────────────────┬───────────────────────┐
│ a   ┆ b   ┆ file_paths            ┆ file_paths            │
│ --- ┆ --- ┆ ---                   ┆ ---                   │
│ i64 ┆ i64 ┆ str                   ┆ str                   │
╞═════╪═════╪═══════════════════════╪═══════════════════════╡
│ 1   ┆ 1   ┆ data\b=1\data.parquet ┆ data\b=1\data.parquet │
│ 2   ┆ 2   ┆ data\b=2\data.parquet ┆ data\b=2\data.parquet │
└─────┴─────┴───────────────────────┴───────────────────────┘

Issue description

If include_file_paths is specified, it includes the same column twice.

Expected behavior

The output should contain only one column with the file paths.

Installed versions

--------Version info---------
Polars:               1.5.0 
Index type:           UInt32
Platform:             Windows-10-10.0.19045-SP0
Python:               3.11.0 (main, Oct 24 2022, 18:26:48) [MSC v.1933 64 bit (AMD64)]

----Optional dependencies----
adbc_driver_manager:  <not installed>
cloudpickle:          <not installed>
connectorx:           <not installed>
deltalake:            <not installed>
fastexcel:            <not installed>
fsspec:               2023.6.0       
gevent:               <not installed>
great_tables:         <not installed>
hvplot:               0.9.2
matplotlib:           3.7.1
nest_asyncio:         1.5.6
numpy:                1.24.3
openpyxl:             <not installed>
pandas:               2.0.3
pyarrow:              12.0.1
pydantic:             2.6.4
pyiceberg:            <not installed>
sqlalchemy:           <not installed>
torch:                <not installed>
xlsx2csv:             <not installed>
xlsxwriter:           <not installed>

[ritchie46]

@nameexhaustion can you take this one?