RFR: Clarified the Affects version section [v4]

[Joakim Nordström]

> Clarification for the [Affects version section](https://openjdk.org/guide/#usage-of-the-rel-na-label)
> 
> * Removed some newlines so things are kept in one paragraph
> * Changed some wording to make the _don'ts_ a bit clearer

Joakim Nordström has updated the pull request incrementally with one additional commit since the last revision:

  Updated rel-na and rel-wnf link

-------------

Changes:
  - all: https://git.openjdk.org/guide/pull/170/files
  - new: https://git.openjdk.org/guide/pull/170/files/2536d310..e55243ee

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=guide&pr=170&range=03
 - incr: https://webrevs.openjdk.org/?repo=guide&pr=170&range=02-03

  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/guide/pull/170.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/170/head:pull/170

PR: https://git.openjdk.org/guide/pull/170