RFR: 7870: JMC 8.3.0 Update Site Pages require changes

[Virag Purnam]

Updated the correct links and details in the update site pages.

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Commit messages:
 - 7870: JMC 8.3.0 Update Site Pages require changes

Changes: https://git.openjdk.org/jmc/pull/426/files
 Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=426&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-7870
  Stats: 9 lines in 4 files changed: 0 ins; 1 del; 8 mod
  Patch: https://git.openjdk.org/jmc/pull/426.diff
  Fetch: git fetch https://git.openjdk.org/jmc pull/426/head:pull/426

PR: https://git.openjdk.org/jmc/pull/426