[css-text-4] Duplicate in the value definition of `white-space`

[yarusome]

In CSS Text 4, the value of white-space is defined as:

normal | pre | nowrap | pre-wrap | pre-line | <'white-space-collapse'> || <'text-wrap'> || <'white-space-trim'>

But nowrap is already included in <'text-wrap'>:

<'text-wrap'> = wrap | nowrap | balance | stable | pretty

[fantasai]

Done! Thanks for reporting!