RFR: 8321325: Remove unused Java_java_awt_MenuComponent_initIDs function

[Sergey Bylokhov]

The Java_java_awt_MenuComponent_initIDs function is empty on Windows and macOS, on linux it has some code but it is unused.

This issue is similar to https://bugs.openjdk.org/browse/JDK-8318091

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Commit messages:
 - date
 - cleanup

Changes: https://git.openjdk.org/jdk/pull/16965/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16965&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321325
  Stats: 81 lines in 6 files changed: 0 ins; 80 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16965.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16965/head:pull/16965

PR: https://git.openjdk.org/jdk/pull/16965