build(deps): bump oras from 0.2.38 to 0.2.39

Bumps [oras](https://github.com/oras-project/oras-py) from 0.2.38 to 0.2.39.
- [Release notes](https://github.com/oras-project/oras-py/releases)
- [Changelog](https://github.com/oras-project/oras-py/blob/main/CHANGELOG.md)
- [Commits](oras-project/oras-py@0.2.38...0.2.39)

---
updated-dependencies:
- dependency-name: oras
  dependency-version: 0.2.39
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -13,7 +13,7 @@ GitPython == 3.1.46    # for manipulating git repos
 unidecode == 1.4.0     # for converting strings to ascii
 coloredlogs == 15.0.1  # for colored logging
 PyYAML == 6.0.3        # for parsing/writing YAML
-oras == 0.2.38         # for OCI stuff in mapper-oci-update
+oras == 0.2.39         # for OCI stuff in mapper-oci-update
 Jinja2 == 3.1.6        # for templating
 rich == 14.3.2         # for rich text formatting
 dtschema == 2025.12     # for checking dts files and dt bindings