remove explicit dependency on junit

Author: hauner

buildSrc/src/main/kotlin/openapiprocessor.test.gradle.kts

@@ -14,7 +14,7 @@ val libs = the<LibrariesForLibs>()
 testing {
     suites {
         val test by getting(JvmTestSuite::class) {
-            useJUnitJupiter(libs.versions.junit.get())
+            useJUnitJupiter()
         }
     }
 }

buildSrc/src/main/kotlin/openapiprocessor.testInt.gradle.kts

@@ -15,7 +15,7 @@ testing {
         val test by getting(JvmTestSuite::class)
 
         val testInt by registering(JvmTestSuite::class) {
-            useJUnitJupiter(libs.versions.junit.get())
+            useJUnitJupiter()
 
             dependencies {
                 implementation(project())