RFR: JDK-8325650: Table of contents scroll timeout not long enough

[Hannes Wallnöfer]

Please review a simple change to increase a timeout value for suppression of scroll-following in the table of contents. This should have no visible effects to the user but may avoid flickering of the table of contents on slower computers. I also replaced a normal inequality operator (`!=`) with a strict one (`!==`) which is better practice when comparing equal types.

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Commit messages:
 - JDK-8325650: Table of contents scroll timeout not long enough

Changes: https://git.openjdk.org/jdk/pull/17811/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17811&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325650
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17811.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17811/head:pull/17811

PR: https://git.openjdk.org/jdk/pull/17811