Bumped Spigot Library Version

A duplication issue has been fixed, can be referenced: https://github.com/JustKato/BetterShulkers/issues/6

Release v1.2.1 · JustKato/BetterShulkers (github.com)
+ Metrics for number of times a shulker box has been opened

+ Updated the plugin to support minecraft 1.21 natively

Simply updated to the latest spigot jar, highly recommended you use this version if you are playing on 1.20.6

* Code Refactoring
+ Different safety function to make sure duplication can't happen
* Testing in 1.20.4

There has been a report that the plugin does not work on versioin 1.20.4 so I have updated the SpigotMC library, hopefully this fixes the issue.

Implemented the [Git Pull Request]( https://github.com/JustKato/BetterShulkers/pull/1) that fixes a dupe bug.

Thank you so much [TheMaxik]( https://github.com/TheMaxik) you're a champ for finding this out and contributing

+ Support for bStats
* Fixed a minor bug