RFR: 8229: Remove unsupported platforms

[Marcus Hirt]

Removing all the older platforms, and changing text to indicate the specific version of Eclipse supported.

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Commit messages:
 - More text
 - Update site text
 - 8229: Remove unsupported platforms

Changes: https://git.openjdk.org/jmc/pull/567/files
  Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=567&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8229
  Stats: 822 lines in 18 files changed: 0 ins; 776 del; 46 mod
  Patch: https://git.openjdk.org/jmc/pull/567.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/567/head:pull/567

PR: https://git.openjdk.org/jmc/pull/567