Hold back eachSumOf for a while: fixups.

Remove unneeded import.

libraries/stdlib/common/src/kotlin/CollectionsH.kt

@@ -158,4 +158,4 @@ header operator fun <K, V> MutableMap<K, V>.set(key: K, value: V): Unit
 
 // from Grouping.kt
 public header fun <T, K> Grouping<T, K>.eachCount(): Map<K, Int>
-public header inline fun <T, K> Grouping<T, K>.eachSumOf(valueSelector: (T) -> Int): Map<K, Int>
+// public header inline fun <T, K> Grouping<T, K>.eachSumOf(valueSelector: (T) -> Int): Map<K, Int>

libraries/stdlib/test/collections/GroupingTest.kt

@@ -1,7 +1,6 @@
 package test.collections
 
 import org.junit.Test
-import java.util.*
 import kotlin.test.*
 
 class GroupingTest {