apacheGH-38823: Fix TestArrowReaderAdHoc.ReadFloat16Files to use new …

…uncompressed files (apache#38825)

### Rationale for this change

[ RUN      ] TestArrowReaderAdHoc.ReadFloat16Files
/arrow/cpp/src/parquet/arrow/arrow_reader_writer_test.cc:4129: Failure
Failed
'reader->ReadTable(&table)' failed with NotImplemented: Support for codec 'snappy' not built
Google Test trace:
/arrow/cpp/src/parquet/arrow/arrow_reader_writer_test.cc:4123: path = /arrow/cpp/submodules/parquet-testing/data/float16_nonzeros_and_nans.parquet
[  FAILED  ] TestArrowReaderAdHoc.ReadFloat16Files (1 ms)
[----------] 6 tests from TestArrowReaderAdHoc (11 ms total)

### What changes are included in this PR?

Use uncompressed files from parquet-testing.

### Are these changes tested?

Make sure the test does not fail.

### Are there any user-facing changes?

No
* Closes: apache#38823

Authored-by: Gang Wu <[email protected]>
Signed-off-by: Gang Wu <[email protected]>