Minor: don't override clean in SourceToClassesMap

build/src/org/jetbrains/kotlin/incremental/IncrementalCacheImpl.kt

@@ -511,10 +511,6 @@ open class IncrementalCacheImpl<Target>(
 
         override fun dumpValue(value: Collection<String>) = value.dumpCollection()
 
-        override fun clean() {
-            storage.keys.forEach { remove(it) }
-        }
-
         private fun remove(path: String) {
             storage.remove(path)
         }

build/src/org/jetbrains/kotlin/incremental/storage/BasicMap.kt

@@ -30,7 +30,7 @@ abstract class BasicMap<K : Comparable<K>, V>(
 ) {
     protected val storage = LazyStorage(storageFile, keyDescriptor, valueExternalizer)
 
-    open fun clean() {
+    fun clean() {
         storage.clean()
     }