Clan skills fixed: avoiding add to list skills already learned

Reported by: Midas, iChaosPaladin, Driad & valanths1990

L2J_Server/java/com/l2jserver/gameserver/data/xml/impl/SkillTreesData.java

@@ -735,7 +735,7 @@ public final class SkillTreesData implements IXmlReader
 				final Skill oldSkill = clan.getSkills().get(skill.getSkillId());
 				if (oldSkill != null)
 				{
-					if (oldSkill.getLevel() < skill.getSkillLevel())
+					if ((oldSkill.getLevel() + 1) == skill.getSkillLevel())
 					{
 						result.add(skill);
 					}