Update kotest to v6.1.9 (#144)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

backend/gradle/libs.versions.toml

@@ -5,7 +5,7 @@ caffeine = "3.2.3"
 dependency_analysis = "3.6.1"
 detekt = "1.23.8"
 gradle_versions_filter = "0.1.16"
-kotest = "6.1.8"
+kotest = "6.1.9"
 kotlin_logging = "8.0.01"
 kotlin = "2.3.20"
 kotlinter = "5.4.2"