RFR: 8313710: jcmd: typo in the documentation of JFR.start and JFR.dump

[Taizo Kurashige]

Hi,

I fixed the typos for JFR.start and JFR.dump.
Acconding to issue's description, there is some typo in JFR.stop documentation, but I couldn't find that. I confirmed that there is no such typo in this repository. So I thought there was no need to fix JFR.stop documentation.

I confirmed that the fixes are reflected and that all of the jdk_jfr tests pass.

Could someone please review it?

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Commit messages:
 - 8313710: jcmd: typo in the documentation of JFR.start and JFR.dump

Changes: https://git.openjdk.org/jdk/pull/16413/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16413&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313710
  Stats: 114 lines in 3 files changed: 0 ins; 0 del; 114 mod
  Patch: https://git.openjdk.org/jdk/pull/16413.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16413/head:pull/16413

PR: https://git.openjdk.org/jdk/pull/16413