Migrate away from allensdk

[IgorTatarnikov]

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Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?
We want to remove allensdk as a dependency to make upgrading to python 3.12 easy, see here

What does this PR do?
Uses the Allen web API to fetch the reconstructed neurons instead of using the allensdk.

References

Closes #67

How has this PR been tested?

All tests pass, I've also tested it locally to make sure we can fetch a variety of files.

Is this a breaking change?

No, I made sure that the DataFrame stored in the neurons attribute of AllenMorphology class has the exact same format.

Does this PR require an update to the documentation?

No

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality (unit & integration)
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit

[IgorTatarnikov]

Tests are currently failing due to neuromorpho being down 😞

[adamltyson]

LGTM, thanks!