Update the name of variorum_get_thermals_example to match the API.

[tpatki]

Description

The example was named variorum-get-node-thermal-json-example which didn't match the associated API, this PR updates the filename for the example to variorum-get-thermals-json-example.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature/architecture support (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Build/CI update

How Has This Been Tested?

Tested build and output on Lassen.

Checklist:

• I have run ./scripts/check-code-format.sh and confirm my code code follows the style guidelines of variorum
• I have added comments in my code
• My changes generate no new warnings (build with -DENABLE_WARNINGS=ON)
• New and existing unit tests pass with my changes

Thank you for taking the time to contribute to Variorum!