GH-47989: [Python][Docs] Add filters_to_expression to Parquet API reference (#48233)

Fixes #47989

Adds `filters_to_expression` to the Parquet autosummary section in `formats.rst`.
Documentation-only change.

* GitHub Issue: #47989

Authored-by: Mo.Aamir Hokabaj <[email protected]>
Signed-off-by: AlenkaF <[email protected]>

Author: Sansfear87

docs/source/python/api/formats.rst

@@ -82,6 +82,7 @@ Parquet Files
    ParquetDataset
    ParquetFile
    ParquetWriter
+   filters_to_expression
    read_table
    read_metadata
    read_pandas