chore: bump sei-config v0.0.18 → v0.0.19

[bdchatham]

Picks up sei-config#27 — reverts default WriteMode to cosmos_only so stable seid v6.5.1 nodes don't break.

Paired with sei-k8s-controller#356 which adds explicit memiavl_only overrides to nightly scenario SND templates.

🤖 Generated with Claude Code

[cursor]

PR Summary

Low Risk
Only lockfile/module version updates; behavior change comes from the upstream default, which this PR intentionally adopts for compatibility.

Overview
Bumps github.com/sei-protocol/sei-config from v0.0.18 to v0.0.19 in go.mod / go.sum, with no other source changes in this repo.

That release aligns with sei-config#27: the default WriteMode is back to cosmos_only, so tooling that resolves config via sei-config (e.g. sidecar ConfigApplyTask) matches stable seid v6.5.1 expectations instead of a memiavl_only default. Nightly memiavl_only overrides are handled separately in sei-k8s-controller.

^{Reviewed by Cursor Bugbot for commit 8e13cbf. Bugbot is set up for automated code reviews on this repo. Configure here.}