RFR: 8332751: Broken link in VirtualMachine.html

[Chris Plummer]

Fixed broken javadoc link. I confirmed that it currently is broken as can be seen in the JDK 22 javadocs:

https://docs.oracle.com/en%2Fjava%2Fjavase%2F22%2Fdocs%2Fapi%2F%2F/jdk.jdi/com/sun/jdi/VirtualMachine.html#allThreads()

Click on the "virtual threads" link within the allThreads() description to see the broken link. 

I verified the fix by building the javadocs and checking that the link now works.

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Commit messages:
 - Fix broken link

Changes: https://git.openjdk.org/jdk/pull/19469/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19469&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332751
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19469.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19469/head:pull/19469

PR: https://git.openjdk.org/jdk/pull/19469