docs: correct typo from copy-paste

src/Discord.Net.Core/Entities/Guilds/PremiumTier.cs

@@ -11,11 +11,11 @@ namespace Discord
         /// </summary>
         Tier1 = 1,
         /// <summary>
-        ///     Used for guilds that have Tier 1 guild boosts.
+        ///     Used for guilds that have Tier 2 guild boosts.
         /// </summary>
         Tier2 = 2,
         /// <summary>
-        ///     Used for guilds that have Tier 1 guild boosts.
+        ///     Used for guilds that have Tier 3 guild boosts.
         /// </summary>
         Tier3 = 3
     }