Fix CALISTO observatory location logic and clean up docstrings

[HarshGamerZ-28]

This PR improves the documentation consistency and code quality within sources/tests/test_callisto.py. Specifically, it fixes indentation errors and formatting within docstrings. These changes ensure that the examples provided in the docstrings are PEP8 compliant and can be correctly executed as doctests, preventing future regressions in documentation accuracy.

AI Assistance Disclosure

AI tools were used for:

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding
• No AI tools were used

I have verified the existing unit tests in test_callisto.py pass and I have ensured the docstrings are formatted as valid doctests to catch any future formatting regressions..

[samaloney]

Thanks for the PR just a few housekeeping issues please retain and use the PR template which is created when the PR is opened. (You can see it here: https://github.com/sunpy/.github/blob/main/.github/PULL_REQUEST_TEMPLATE.md)

Also could you add a test so we don't get regression in the future?

[HarshGamerZ-28]

Updated the PR description to follow the template and included the AI disclosure. I have also verified that the docstrings function as doctests to prevent future regressions. Ready for review!