Avoid check on MZ_OPEN_MODE_READWRITE (being composed of READ | WRITE)

[carlopi]

I checked implementation MZ_OPEN_MODE_READWRITE is a combination of READ bit and WRITE bit ([example](https://pub.dev/documentation/flutter_minizip_ffi_bindings/latest/flutter_minizip_ffi_bindings/MZ_OPEN_MODE_READWRITE-constant.html, 1 | 2 = 3)

That means that MZ_OPEN_MODE_READWRITE & flags will be true if EITHER read or write are set, this in turns make file opened for reading with a flags connected to writing.

This I think trigger failures like:

================================================================================
Query unexpectedly failed (D:/a/duckdb/duckdb/build/release/_deps/excel_extension_fc-src/test/sql/excel/xlsx/read_sparse.test:31)
================================================================================
select * FROM read_xlsx('test/data/xlsx/sparse.xlsx', header = false, range = 'W801:W801');
================================================================================
Actual result:
IO Error: Cannot open file "test/data/xlsx/sparse.xlsx": The process cannot access the file because it is being used by another process.

and problem while using in duckdb-wasm (that due to weird file system requires either write or read permissions).

[carlopi]

Not ready, given this fails Windows CI, but the way I read the errors is that basically when first writing then reading a file, like in https://github.com/duckdb/duckdb-excel/blob/main/test/sql/excel/xlsx/bignum.test, there is something off with lifetimes of the FileHandles in Windows. I think FileHandle somehow survive the query duration / are cached, but unsure.

Help might be handy in bringing this in.