MAINT: Update deprecated 'Dataset.dims' usage to 'Dataset.sizes'

[Aadarsh-Govada]

Description

The current usage of 'Dataset.dims' will soon be deprecated. The return type of Dataset.dims will be changed to return a set of dimension names in future, in order to be more consistent with DataArray.dims. This PR replaces the current uses of 'Dataset.dims' with 'Dataset.sizes'.

Type of change

Maintenance

How Has This Been Tested?

Test Configuration:

• Operating system: GitHub Actions Ubuntu, Windows, and MacOS
• Version number: Python 3.X

Checklist:

• Make sure you are merging into the develop (not main) branch
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• Add a note to CHANGELOG.md, summarizing the changes
• Update zenodo.json file for new code contributors