RFR: 8253148: Fix terminology in align_down comment

[Kim Barrett]

Please review this trivial terminology change in a comment.  This was supposed to be part of JDK-8247910, but I forgot
to push this comment change before integrating.

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Commit messages:
 - Change lognot => logical_not in comment

Changes: https://git.openjdk.java.net/jdk/pull/166/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=166&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253148
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/166.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/166/head:pull/166

PR: https://git.openjdk.java.net/jdk/pull/166