RFR: 8293028: Remove GenCollectedHeap::handle_failed_promotion

[Albert Mingkun Yang]

Trivial change of removing dead code.

Test: build

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Commit messages:
 - trivial

Changes: https://git.openjdk.org/jdk/pull/10063/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10063&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293028
  Stats: 9 lines in 1 file changed: 0 ins; 9 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10063.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10063/head:pull/10063

PR: https://git.openjdk.org/jdk/pull/10063