[bug-63533] fix javadoc that refers to horisontalPdi

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1862382 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/poi/ss/util/ImageUtils.java

@@ -112,7 +112,7 @@ public class ImageUtils {
      * Return the the "effective" dpi calculated as <code>25.4/HorizontalPixelSize</code>
      * and <code>25.4/VerticalPixelSize</code>.  Where 25.4 is the number of mm in inch.
      *
-     * @return array of two elements: <code>{horisontalPdi, verticalDpi}</code>.
+     * @return array of two elements: <code>{horizontalDpi, verticalDpi}</code>.
      * {96, 96} is the default.
      */
     public static int[] getResolution(ImageReader r) throws IOException {