Use version references for plugins

gradle/libs.versions.toml

@@ -5,6 +5,7 @@ junit-jupiter = "5.10.2"
 platform-launcher = "1.10.2"
 kotlinx-coroutines-core-jvm = "1.8.0"
 kotlin = "1.9.24"
+coveralls-jacoco = "1.2.20"
 
 [libraries]
 assertj-core = { module = "org.assertj:assertj-core", version.ref = "assertj-core" }
@@ -17,5 +18,5 @@ kotlin-stdlib = { module = "org.jetbrains.kotlin:kotlin-stdlib", version.ref = "
 kotlin-test-junit5 = { module = "org.jetbrains.kotlin:kotlin-test-junit5", version.ref = "kotlin" }
 
 [plugins]
-kotlin-jvm = { id = "org.jetbrains.kotlin.jvm", version = "1.9.24" }
-coveralls-jacoco = { id = "com.github.nbaztec.coveralls-jacoco", version = "1.2.20" }
+kotlin-jvm = { id = "org.jetbrains.kotlin.jvm", version.ref = "kotlin" }
+coveralls-jacoco = { id = "com.github.nbaztec.coveralls-jacoco", version.ref = "coveralls-jacoco" }