RFR: 8263203: jconsole Online User Guide has wrong URL

[Chris Plummer]

The URL for the users guide, referenced from both the About dialog and from the "Help -> Online Users Guide" menu item, has not functioned for a few releases due the restructuring of the JDK online docs. This PR fixes the URL. Note I also filed JDK-8268351 to get rid of the URL, but for 17 I prefer to just fix the URL.

BTW, the change to MANAGE_HOTSPOT_MBEANS_IN_COLON_ is just my editor automatically getting rid of an extra space at the end of the line.

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Commit messages:
 - Update URL for jconsole Users Guide

Changes: https://git.openjdk.java.net/jdk/pull/4399/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4399&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263203
  Stats: 7 lines in 3 files changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4399.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4399/head:pull/4399

PR: https://git.openjdk.java.net/jdk/pull/4399