Bump okio from 3.13.0 to 3.15.0 (#312)

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -3,7 +3,7 @@ kotlin = "2.1.21"
 kotest = "6.0.0.M3"
 detekt = "1.23.8"
 ktlint = "1.1.0"
-okio = "3.13.0"
+okio = "3.15.0"
 serialization = "1.8.1"
 benchmark = "0.4.14"
 openapi = "2025.3"