RFR: Minor cleanups after the JBS re-write [v7]

[Jesper Wilhelmsson]

> Using markdown tables instead of html tables.
> Added a separate style for JBS values.
> Minor language fixes to make it the same style as the rest of the guide.
> Clarified some sentences.
> Added the label jep-superseded to the dictionary.

Jesper Wilhelmsson has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - Merge branch 'master' into cleanups
 - Fixed comments from Iris
 - Fixed the "bad backport created" section for the new backport policy
 - Added reference to "I have a patch" from "working with pull requests"
 - Added note about affects version
 - Updated text to accomodate for backports to feature relseases in rampdown
 - Minor cleanups after the JBS re-write

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Changes: https://git.openjdk.org/guide/pull/106/files
 Webrev: https://webrevs.openjdk.org/?repo=guide&pr=106&range=06
  Stats: 232 lines in 6 files changed: 25 ins; 88 del; 119 mod
  Patch: https://git.openjdk.org/guide/pull/106.diff
  Fetch: git fetch https://git.openjdk.org/guide.git pull/106/head:pull/106

PR: https://git.openjdk.org/guide/pull/106