fix comment

Author: sameeragarwal

sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/ColumnarAggMapCodeGenerator.scala

@@ -21,10 +21,10 @@ import org.apache.spark.sql.catalyst.expressions.codegen.CodegenContext
 import org.apache.spark.sql.types.StructType
 
 /**
- * This is a helper object to generate an append-only single-key/single value aggregate hash
- * map that can act as a 'cache' for extremely fast key-value lookups while evaluating aggregates
- * (and fall back to the `BytesToBytesMap` if a given key isn't found). This is 'codegened' in
- * TungstenAggregate to speed up aggregates w/ key.
+ * This is a helper class to generate an append-only aggregate hash map that can act as a 'cache'
+ * for extremely fast key-value lookups while evaluating aggregates (and fall back to the
+ * `BytesToBytesMap` if a given key isn't found). This is 'codegened' in TungstenAggregate to speed
+ * up aggregates w/ key.
  *
  * It is backed by a power-of-2-sized array for index lookups and a columnar batch that stores the
  * key-value pairs. The index lookups in the array rely on linear probing (with a small number of