refactor: remove use of deprecated DateTime::from_utc

[ComputerDruid]

[!IMPORTANT] Refactor to remove deprecated DateTime::from_utc and update chrono version in Cargo.toml.

• Refactor:
  • Replace DateTime::from_utc with into() in aw-client-rust/tests/test.rs for timestamp conversion.
• Dependencies:
  • Update chrono version from 0.4 to 0.4.7 in Cargo.toml.

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