gh-146579: _zstd: Fix decompression options dict error message

[cuiweixie]

Summary

Fix the TypeError string in _zstd_set_d_parameters: it incorrectly said
compression options dictionary when validating decompression option keys.

Test plan

• No behavior change beyond the error text; optional manual check by passing an
  invalid key type to decompression options.

• Issue: _zstd: Fix decompression options dict error message #146579

[serhiy-storchaka]

I am not sure this is a bug. Should not the compression options dictionary be the same for compression and decompression? They are compression options which should be passed to decompressor to inform what options were used during compression.

[picnixz]

Should not the compression options dictionary be the same for compression and decompression?

They actually differ:

• https://docs.python.org/3/library/compression.zstd.html#compression.zstd.CompressionParameter
• https://docs.python.org/3/library/compression.zstd.html#compression.zstd.DecompressionParameter

[serhiy-storchaka]

You are right. This check is especially to check that they are not mixed.