RFR: JDK-8262892: minor typo in implSpec comment

[Jonathan Gibbons]

Please review a trivial fix to insert a missing word.

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Commit messages:
 - JDK-8262892: minor typo in implSpec comment

Changes: https://git.openjdk.java.net/jdk/pull/2798/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2798&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262892
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2798.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2798/head:pull/2798

PR: https://git.openjdk.java.net/jdk/pull/2798