Fixes to the LayoutNG article (#8100)
Fixes to the LayoutNG article (#8100)

In the *LayoutNG* article,

- Added missing periods/commas.
- Fixed a broken word due to a line-break.
- Removed hyphens in "For elements that size-to-content".
- Removed underscores from "_T_", which were probably added to make the T italic, but this doesn't work because we're inside of a block-level element (`<figcaption>`). However, rather than wrapping the T in `<i>`, it's probably better to leave it roman type so it's consistent with the way it is mentioned in a paragraph above.
- Removed the misplaced space in "Layout NG".
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