RFR: 8320334: Reflow markdown in testing.md

Fri Nov 17 16:47:43 UTC 2023

In preparation for textual updates, the markdown in testing.md is reflowed so line lengths of 80 is respected, wherever possible. 

Note that is is correct  that the testing.html file is unchanged (and indeed a sign that only markdown line breaks have been modified).

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Commit messages:
 - 8320334: Reflow markdown in testing.md

Changes: https://git.openjdk.org/jdk/pull/16712/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16712&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320334
  Stats: 113 lines in 1 file changed: 5 ins; 9 del; 99 mod
  Patch: https://git.openjdk.org/jdk/pull/16712.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16712/head:pull/16712

PR: https://git.openjdk.org/jdk/pull/16712