Fix: specify list positional argument within search.categorical

[Doel10]

What this PR does / why we need it:
katib.search.categorical() incorrectly constructs V1beta1FeasibleSpace by passing the list value as positional argument mapping it to the distribution argument instead of list argument.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #2625

Checklist:

• Docs included if any changes are user facing

[google-oss-prow]

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