build(deps): bump dtschema from 2025.2 to 2025.6.1

Bumps [dtschema](https://github.com/devicetree-org/dt-schema) from 2025.2 to 2025.6.1.
- [Release notes](https://github.com/devicetree-org/dt-schema/releases)
- [Commits](devicetree-org/dt-schema@v2025.02...v2025.06.1)

---
updated-dependencies:
- dependency-name: dtschema
  dependency-version: 2025.6.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -16,5 +16,5 @@ PyYAML == 6.0.2        # for parsing/writing YAML
 oras == 0.2.33         # for OCI stuff in mapper-oci-update
 Jinja2 == 3.1.6        # for templating
 rich == 14.0.0         # for rich text formatting
-dtschema == 2025.2     # for checking dts files and dt bindings
+dtschema == 2025.6.1     # for checking dts files and dt bindings
 yamllint == 1.37.1     # for checking dts files and dt bindings