Fix schema.core/defmethod linting for vectors dispatch-values

[leoiacovini]

Closes: #1174

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I preferred to go with the approach to track the fn-sym and index instead of trying to infer when the vector was supposed to be the arguments or the dispatch value (for any schema.core macro) because the inferring logic was going to be more complex (in the code or even computationally) and would probably still have some bugs in corner cases when using the :- keyword inside function bodies

[borkdude]

Thanks!