Typo: `spacing_mark` spelled `spaing_mark`

[midrare]

I found a small typo.

LEXY_UNICODE_CATEGORY(Mc, spaing_mark)
                            -^-

[bhanuprakasheagala]

Hi @midrare, Hope it's okay to merge the PR as it's only typo fix.

[foonathan]

Thanks! Fixed.