RFR: 8264610: Number.{byteValue, shortValue} spec should use @implSpec

[Joe Darcy]

Please review this small code change and its accompanying CSR:

 https://bugs.openjdk.java.net/browse/JDK-8264610

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Commit messages:
 - Update second method.
 - 8264609: Number.shortValue spec should use @implSpec

Changes: https://git.openjdk.java.net/jdk/pull/3314/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3314&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264610
  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3314.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3314/head:pull/3314

PR: https://git.openjdk.java.net/jdk/pull/3314