Update model:core to 1.5.4

[scala-steward]

Updates com.softwaremill.sttp.model:core from 1.5.3 to 1.5.4. GitHub Release Notes - Version Diff

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Adjust future updates

Add this to your `.scala-steward.conf` file to ignore future updates of this dependency: ``` updates.ignore = [ { groupId = "com.softwaremill.sttp.model", artifactId = "core" } ] ``` Or, add this to slow down future updates of this dependency: ``` dependencyOverrides = [{ pullRequests = { frequency = "@monthly" }, dependency = { groupId = "com.softwaremill.sttp.model", artifactId = "core" } }] ```

labels: library-update, early-semver-patch, semver-spec-patch, commit-count:1