RFR: 8253344: Remove unimplemented Arguments::check_gc_consistency

[Aleksey Shipilev]

Looks like a leftover from JDK-8199925 that removed the definition, but left the declaration back.

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

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Commit messages:
 - 8253344: Remove unimplemented Arguments::check_gc_consistency

Changes: https://git.openjdk.java.net/jdk/pull/240/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=240&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253344
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/240.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/240/head:pull/240

PR: https://git.openjdk.java.net/jdk/pull/240