Unify the criteria which are used to consider a font to be bold.

Its font weight should be more than 500.

DEVSIX-2777

Author: ars18wrw

layout/src/main/java/com/itextpdf/layout/font/FontCharacteristics.java

@@ -121,7 +121,7 @@ public boolean isItalic() {
     }
 
     public boolean isBold() {
-        return isBold || fontWeight > 600;
+        return isBold || fontWeight > 500;
     }
 
     public boolean isMonospace() {