set_sorted(COL) before head blocks N_ROWS pushdown, also seems to drop the setting column as sorted

[kszlim]

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
from tempfile import TemporaryDirectory
from pathlib import Path

df = pl.DataFrame({"a": list(range(10000))})
with TemporaryDirectory() as tmp:
    tmp = Path(tmp)
    for x in range(5):
        df.write_parquet(tmp / f"{x}.parquet")

    ldf = pl.scan_parquet(tmp / "*.parquet")
    ldf_sort_first = ldf.set_sorted("a").head(5)
    print(ldf.explain())

    ldf_sort_later = ldf.head(5).set_sorted("a")
    print(ldf_sort_later.explain())

Log output

Parquet SCAN 5 files: first file: /tmp/tmp486vqawl/0.parquet
  PROJECT */1 COLUMNS

 WITH_COLUMNS:
 [col("a").set_sorted()]

    Parquet SCAN 5 files: first file: /tmp/tmp486vqawl/0.parquet
    PROJECT */1 COLUMNS
    N_ROWS: 5

### Issue description

As described in title

### Expected behavior

Should have identical query plans

### Installed versions

--------Version info---------
Polars: 0.20.3
Index type: UInt32
Platform: Linux-6.2.6-76060206-generic-x86_64-with-glibc2.35
Python: 3.10.9 (main, Jan 11 2023, 15:21:40) [GCC 11.2.0]

----Optional dependencies----
adbc_driver_manager:
cloudpickle: 2.2.1
connectorx:
deltalake: 0.10.0
fsspec: 2023.4.0
gevent:
hvplot: 0.8.4
matplotlib: 3.7.1
numpy: 1.24.3
openpyxl:
pandas: 1.5.3
pyarrow: 12.0.1
pydantic: 1.10.9
pyiceberg:
pyxlsb:
sqlalchemy:
xlsx2csv:
xlsxwriter: ```