Remove comment about unknown built-in style

Removed comment about unknown built-in style from getTableStyle method.
diff --git a/poi-ooxml/src/main/java/org/apache/poi/xssf/model/StylesTable.java b/poi-ooxml/src/main/java/org/apache/poi/xssf/model/StylesTable.java
index abab993..1eb86f2 100644
--- a/poi-ooxml/src/main/java/org/apache/poi/xssf/model/StylesTable.java
+++ b/poi-ooxml/src/main/java/org/apache/poi/xssf/model/StylesTable.java
@@ -841,7 +841,6 @@
      * @return defined style, either explicit or built-in, or null if not found
      *
      * @since 3.17 beta 1
-     * unknown built-in style
      */
     public TableStyle getTableStyle(String name) {
         if (name == null) return null;