fix: make sure our own damage isn't stopped by knocked invulnerability

Signed-off-by: Octol1ttle <l1ttleofficial@outlook.com>

src/main/java/ru/octol1ttle/knockdowns/common/KnockdownsCommonEventListener.java

@@ -85,6 +85,7 @@ public class KnockdownsCommonEventListener {
         knocked.clearElytraFlying();
 
         if (allPlayersKnocked(server, knocked)) {
+            data.setTicksKnocked((int) (KNOCKED_INVULNERABILITY_TICKS + 1));
             knocked.attackEntityFrom(DamageSource.GENERIC, knocked.getMaxHealth());
             return;
         }