[jdk21u-dev] RFR: 8318962: Update ProcessTools javadoc with suggestions in 8315097

[Goetz Lindenmaier]

I backport this to simplify further backports.

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Commit messages:
 - Backport 7e4cb2f09d1219c6ba7bfa77be831a7c7c9b055a

Changes: https://git.openjdk.org/jdk21u-dev/pull/457/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=457&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318962
  Stats: 70 lines in 1 file changed: 42 ins; 4 del; 24 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/457.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/457/head:pull/457

PR: https://git.openjdk.org/jdk21u-dev/pull/457