Fix the problem that getHeight() is smaller than the actual value

`+ getLeading()` was removed in this commit: 5a18307eb0 (diff-4cd687c3da36fff3b21d074a27f7bac176c2845b43d37eca3af37fb920baf32cL73)
I can't find a reason for the removal.
Due to the lack of leading height, the height obtained by this method is much smaller than the actual height (Test with Chinese characters).

poi/src/main/java/org/apache/poi/sl/draw/DrawTextFragment.java

      * @return full height of this text run which is sum of ascent, descent and leading
      */
     public float getHeight(){
-        double h = layout.getAscent() + layout.getDescent();
+        double h = layout.getAscent() + layout.getDescent() + getLeading();
         return (float)h;
     }