RFR: 8279505: Update documentation for RETRY_COUNT and REPEAT_COUNT

[Aleksey Shipilev]

Following up on suggestion here: 
 https://github.com/openjdk/jdk/pull/6720#discussion_r778457819

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Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/6964/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6964&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279505
  Stats: 8 lines in 2 files changed: 4 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6964.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6964/head:pull/6964

PR: https://git.openjdk.java.net/jdk/pull/6964