[css-text] Error in text-spacing: space-end description

[MurakamiShinyu]

https://drafts.csswg.org/css-text-4/#valdef-text-spacing-space-end

space-end
Set fullwidth opening punctuation with full-width glyphs (spaced) at the start of each line.

This should be:

Set fullwidth closing punctuation with full-width glyphs (spaced) at the end of each line.

[frivoal]

pinging editors @fantasai @kojiishi @astearns

[frivoal]

Not an editor of this spec, but fixed it anyway.