RFR: 8327240: Remove unused Tier2CompileThreshold/Tier2BackEdgeThreshold product flags

[Sonia Zaldana Calles]

Hi all, 

This PR removes the unused options ```Tier2CompileThreshold``` and ```Tier2BackEdgeThreshold```. 

Testing: 
- [x] Verified unrecognized option error is reported after removing options. 

Thanks, 
Sonia

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Commit messages:
 - 8327240: Remove unused Tier2CompileThreshold/Tier2BackEdgeThreshold product flags

Changes: https://git.openjdk.org/jdk/pull/18904/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18904&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327240
  Stats: 8 lines in 1 file changed: 0 ins; 8 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18904.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18904/head:pull/18904

PR: https://git.openjdk.org/jdk/pull/18904