RFR: 8253348: Remove unimplemented JNIHandles::initialize

[Aleksey Shipilev]

Seems to be a left-over from JDK-8227053 that removed the definition, but left the declaration behind.

Testing:
  - [x] Linux x86_64 fastdebug build
  - [x] Text search for `JNIHandles::initialize` in `src/hotspot`

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Commit messages:
 - 8253348: Remove unimplemented JNIHandles::initialize

Changes: https://git.openjdk.java.net/jdk/pull/243/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=243&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253348
  Stats: 3 lines in 1 file changed: 0 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/243.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/243/head:pull/243

PR: https://git.openjdk.java.net/jdk/pull/243