RFR: 8283788: Remove unused VM_DeoptimizeAll::_dependee

[Aleksey Shipilev]

SonarCloud complains the `VM_DeoptimizeAll::_dependee` field is not initialized. In fact, it is not used at all and can be removed.

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Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/7993/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7993&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283788
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7993.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7993/head:pull/7993

PR: https://git.openjdk.java.net/jdk/pull/7993