fix: fix miss makezero bug

[alingse]

- Summary

I was running github actions to run linter makezero for top github golang repos.

see issues https://github.com/alingse/go-linter-runner/issues/1

and the github actions output https://github.com/alingse/go-linter-runner/actions/runs/9242969110/job/25426483234

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append to slice `xcols` with non-zero initialized length at https://github.com/netlify/gotrue/blob/master/storage/dial.go#L76:11
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- Test plan

- Description for the changelog

fix the bug of getExcludedColumns

- A picture of a cute animal (not mandatory but encouraged) 🐢