Removed superfluous recalculation call; Fixes BUKKIT-3728

The permission attachment interface provides two methods each for setting
and unsetting permissions. Each one also provides an extra call to the
recalculatePermissions() method on the permissible, which degrades
performance.

This commit removes the duplicate call to recalculate permissions.

src/main/java/org/bukkit/permissions/PermissionAttachment.java

@@ -90,7 +90,6 @@ public class PermissionAttachment {
      */
     public void setPermission(Permission perm, boolean value) {
         setPermission(perm.getName(), value);
-        permissible.recalculatePermissions();
     }
 
     /**
@@ -114,7 +113,6 @@ public class PermissionAttachment {
      */
     public void unsetPermission(Permission perm) {
         unsetPermission(perm.getName());
-        permissible.recalculatePermissions();
     }
 
     /**