fix: StringUtils#rtrim

assira/src/main/java/net/ranides/assira/text/StringUtils.java

@@ -431,7 +431,7 @@ public final class StringUtils {
             return "";
         }
         int offset = text.length() - 1;
-        while(offset >= 0 && Character.isWhitespace(text.charAt(offset)) ) { 
+        while(offset >= 0 && cp.test(text.charAt(offset)) ) {
 			offset--; 
 		}
         return text.substring(0, offset+1);