Chore: Remove 1.21 support because buildtools sucks

Author: Skullians

.github/workflows/build.yml

@@ -54,10 +54,6 @@ jobs:
         if: steps.cache-maven.outputs.cache-hit != 'true'
         run: if [ ! -f "~/.m2/repository/org/bukkit/craftbukkit/1.20.6-R0.1-SNAPSHOT/craftbukkit-1.20.6-R0.1-SNAPSHOT-remapped-mojang.jar" ]; then cd ~/spigot-buildtools && java -jar BuildTools.jar --rev 1.20.6 --remapped --compile CRAFTBUKKIT; fi
 
-      - name: Install CraftBukkit 1.21
-        if: steps.cache-maven.outputs.cache-hit != 'true'
-        run: if [ ! -f "~/.m2/repository/org/bukkit/craftbukkit/1.21-R0.1-SNAPSHOT/craftbukkit-1.21-R0.1-SNAPSHOT-remapped-mojang.jar" ]; then cd ~/spigot-buildtools && java -jar BuildTools.jar --rev 1.21 --remapped --compile CRAFTBUKKIT; fi
-
       - name: Install CraftBukkit 1.21.1
         if: steps.cache-maven.outputs.cache-hit != 'true'
         run: if [ ! -f "~/.m2/repository/org/bukkit/craftbukkit/1.21.1-R0.1-SNAPSHOT/craftbukkit-1.21.1-R0.1-SNAPSHOT-remapped-mojang.jar" ]; then cd ~/spigot-buildtools && java -jar BuildTools.jar --rev 1.21.1 --remapped --compile CRAFTBUKKIT; fi