chore(deps): bump net.fabricmc:sponge-mixin from 0.15.2+mixin.0.8.7 to 0.15.4+mixin.0.8.7 - #30

Submitted dependency-graph-reports/dynamicdependency-graphauto-submission-submit-gradle.json: The snapshot was accepted, but it is not for the default branch. It will not update dependency results for the repository.

Using Java 21 (temurin) with Gradle (using wrapper)