Bump org.mockito:mockito-core from 5.7.0 to 5.15.2

Author: nstdio

buildSrc/src/main/kotlin/io.github.nstdio.http.ext.test-conventions.gradle.kts

@@ -64,7 +64,7 @@ mapOf(
 val junitVersion = "5.11.4"
 val assertJVersion = "3.27.3"
 val kotestAssertionsVersion = "5.8.0"
-val mockitoVersion = "5.7.0"
+val mockitoVersion = "5.15.2"
 val jsonPathAssertVersion = "2.7.0"
 val slf4jVersion = "1.7.36"
 val jacksonVersion = "2.18.2"