[Feature] Replace RewardClipping with SignTransform in Atari examples

[albertbou92]

Description

In practice does not change the value for Atari envs because there are no rewards smaller than abs(1.0), but the original implementations of the examples compute the sign of the rewards instead of clipping it. Would close this issue: #1777

Motivation and Context

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You can use the syntax close #15213 if this solves the issue #15213

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• Example (update in the folder of examples)

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[pytorch-bot]

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✅ You can merge normally! (4 Unrelated Failures)

As of commit d76f6cf with merge base 5f82601 ():

FLAKY - The following jobs failed but were likely due to flakiness present on trunk:

• Continuous Benchmark (PR) / CPU Pytest benchmark (gh)
  Workflow failed! Resource not accessible by integration
• Continuous Benchmark (PR) / GPU Pytest benchmark (gh)
  Workflow failed! Resource not accessible by integration
• Habitat Tests on Linux / tests (3.9, 11.6) / linux-job (gh)
  RuntimeError: Command docker exec -t ad39865abdbcb272e3b2250fb91cd815e90729749132b58d8cd720aacce17f90 /exec failed with exit code 139
• Unit-tests on Windows / unittests-gpu / windows-job (gh)
  ##[error]The operation was canceled.

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[vmoens]

Thanks! I'd get a couple of training loops done with and without this change before merging if that's ok!