RFR: 6753: JMC Help Documentation requires corrections

[Suchita Chaturvedi]

This PR updates the old instructions of starting JMC when it was bundled as part of jdk.

Please review the change and let me know if there are any changes required.

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Commit messages:
 - 6753: JMC Help Documentation requires corrections

Changes: https://git.openjdk.java.net/jmc/pull/212/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=212&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6753
  Stats: 7 lines in 1 file changed: 0 ins; 1 del; 6 mod
  Patch: https://git.openjdk.java.net/jmc/pull/212.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/212/head:pull/212

PR: https://git.openjdk.java.net/jmc/pull/212