Set correct base classloader for REPL evaluation

the contributed partial fix of KT-35925 set it to the system classloader
which brought in many cases the compiler CP into the evaluation and lead
to the problems like KT-40898. This fix set it to the extension/platform
classloader, which preserves (partial) fix of the KT-35925 and do not
bring the compiler jar into the REPL evaluation classpath.

#KT-40898 fixed

plugins/scripting/scripting-compiler/src/org/jetbrains/kotlin/scripting/compiler/plugin/repl/ReplInterpreter.kt

@@ -42,7 +42,7 @@ class ReplInterpreter(
         ReplClassLoader(
             URLClassLoader(
                 classpathRoots.map { it.toURI().toURL() }.toTypedArray(),
-                ClassLoader.getSystemClassLoader()
+                ClassLoader.getSystemClassLoader()?.parent
             )
         )