[BUG] Fix Levy distribution tags: move mean/var to capabilities:undefined and add missing distr:paramtype tag

[ANANYA542]

The Levy distribution has infinite mean and infinite variance. However, it incorrectly listed mean and var under capabilities:exact instead of capabilities:undefined. This PR corrects the tags dictionary and adds the missing distr:paramtype: parametric tag.

Reference Issues/PRs

fixes #941

What does this implement/fix? Explain your changes.

The Lévy distribution has infinite mean and infinite variance. However, skpro/distributions/levy.py incorrectly listed mean and var under "capabilities:exact". This is misleading because the values returned are simply inf — framework components relying on this tag might assume the exact calculation yields finite, usable numbers.
This PR makes three changes:
Removes mean and var from "capabilities:exact"
Adds "capabilities:undefined": ["mean", "var"], consistent with how Cauchy handles its undefined mean
Adds the missing "distr:paramtype": "parametric" tag, required for framework functions like to_df()

Does your contribution introduce a new dependency? If yes, which one?

no

What should a reviewer concentrate their feedback on?

1.Verifying the mathematical correctness of moving mean and var to capabilities:undefined
2.Confirming the tag formatting is consistent with how other distributions like Cauchy declare undefined capabilities

Did you add any tests for the change?

No new tests were added. The existing automated test framework in skpro/distributions/tests/test_all_distrs.py will automatically validate against the updated capabilities for the Levy distribution.

Any other comments?

A screenshot of the fix applied locally is attached below.

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