[MINOR] Minor update for document

Two minor doc errors in `BytesToBytesMap` and `UnsafeRow`.

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #5906 from viirya/minor_doc and squashes the following commits:

27f9089 [Liang-Chi Hsieh] Minor update for doc.

sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/UnsafeRow.java

@@ -145,7 +145,7 @@ public final class UnsafeRow implements MutableRow {
 
   private void assertIndexIsValid(int index) {
     assert index >= 0 : "index (" + index + ") should >= 0";
-    assert index < numFields : "index (" + index + ") should <= " + numFields;
+    assert index < numFields : "index (" + index + ") should < " + numFields;
   }
 
   @Override

unsafe/src/main/java/org/apache/spark/unsafe/map/BytesToBytesMap.java

@@ -351,9 +351,9 @@ public final class BytesToBytesMap {
      * As an example usage, here's the proper way to store a new key:
      * <p>
      * <pre>
-     *   Location loc = map.lookup(keyBaseOffset, keyBaseObject, keyLengthInBytes);
+     *   Location loc = map.lookup(keyBaseObject, keyBaseOffset, keyLengthInBytes);
      *   if (!loc.isDefined()) {
-     *     loc.putNewKey(keyBaseOffset, keyBaseObject, keyLengthInBytes, ...)
+     *     loc.putNewKey(keyBaseObject, keyBaseOffset, keyLengthInBytes, ...)
      *   }
      * </pre>
      * <p>