Add warning to TextRendererTest about future dev

DEVSIX-1385

Author: Benoit Lagae

layout/src/test/java/com/itextpdf/layout/renderer/TextRendererTest.java

@@ -108,6 +108,10 @@ public void setTextException() {
         Assert.assertEquals(val, rend.getText().toString());
     }
 
+    /**
+     * This test assumes that absolute positioning for {@link Text} elements is
+     * not supported. Adding this support is the subject of DEVSIX-1393.
+     */
     @Test
     @LogMessages(messages = {
             @LogMessage(messageTemplate = LogMessageConstant.FONT_PROPERTY_MUST_BE_PDF_FONT_OBJECT)