[DynInst_API:] [dyninst/dyninst] 9c00fd: Remove Singleton.h (#1592)

[Tim Haines <noreply@xxxxxxxxxx>]

  Branch: refs/heads/master
  Home:   https://github.com/dyninst/dyninst
  Commit: 9c00fd5bb5b593a95af9efd5b1b5f508f0a9e568
      https://github.com/dyninst/dyninst/commit/9c00fd5bb5b593a95af9efd5b1b5f508f0a9e568
  Author: Tim Haines <thaines.astro@xxxxxxxxx>
  Date:   2023-10-26 (Thu, 26 Oct 2023)

  Changed paths:
    M common/CMakeLists.txt
    R common/src/Singleton.h
    M instructionAPI/src/Operation.C
    M instructionAPI/src/Register.C
    M instructionAPI/src/Ternary.C

  Log Message:
  -----------
  Remove Singleton.h (#1592)

It's not used anymore.