RFR: 8253633: Remove unimplemented TieredThresholdPolicy::set_carry_if_neccessary

[Aleksey Shipilev]

The definition seems to be removed with JDK-8203883, but the declaration was left behind.

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

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Commit messages:
 - 8253633: Remove unimplemented TieredThresholdPolicy::set_carry_if_necessary

Changes: https://git.openjdk.java.net/jdk/pull/355/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=355&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253633
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/355.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/355/head:pull/355

PR: https://git.openjdk.java.net/jdk/pull/355