Fix growTable function for HashMap

When tranisitioning from dense to hashing, we grow the table more than usual
since otherwise we'd have to grow it again at the very next addEntry. The
condition for this was wrong for HashMaps.

Author: odersky

compiler/src/dotty/tools/dotc/util/GenericHashMap.scala

@@ -156,7 +156,7 @@ abstract class GenericHashMap[Key, Value]
   protected def growTable(): Unit =
     val oldTable = table
     val newLength =
-      if oldTable.length == DenseLimit then DenseLimit * 2 * roundToPower(capacityMultiple)
+      if table.length == DenseLimit * 2 then table.length * roundToPower(capacityMultiple)
       else table.length
     allocate(newLength)
     copyFrom(oldTable)