Use AWS_REGION secret

[AlexRuiz7]

Description

This PR updates the build.yml workflow to use the AWS_REGION secret, replacing the hard-coded value.

Issues Resolved

Closes #208

Check List

• [ ] New functionality includes testing.
  • [ ] All tests pass
• [ ] New functionality has been documented.
  • [ ] New functionality has javadoc added
• [ ] Failing checks are inspected and point to the corresponding known issue(s) (See: Troubleshooting Failing Builds)
• [ ] Commits are signed per the DCO using --signoff
• [ ] Commit changes are listed out in CHANGELOG.md file (See: Changelog)
• [ ] Public documentation issue/PR created

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[AlexRuiz7]

Successful workflow runs:

• deb
• rpm