Drop 1.16.5 support to use Mojang mappings

Because there is no option to create a `remapped-mojang` artifact for 1.16.5 and the whole point of the scripts is to save me time, 1.16.5 support is being removed earlier than usual.

Also fixes issues with NMS-based shulker collision check.
Closes #36

scripts/install_spigot_dependencies.sh

@@ -36,12 +36,12 @@ echo Found Spigot dependencies: "${versions[@]}"
 for version in "${versions[@]}"; do
   set -e
   exit_code=0
-  mvn dependency:get -Dartifact=org.spigotmc:spigot:"$version" -q -o || exit_code=$?
+  mvn dependency:get -Dartifact=org.spigotmc:spigot:"$version":remapped-mojang -q -o || exit_code=$?
   if [ $exit_code -ne 0 ]; then
     echo Installing missing Spigot version "$version"
     revision=${version%%-R*}
     get_buildtools
-    java -jar $buildtools -rev "$revision"
+    java -jar $buildtools -rev "$revision" --remapped
   else
     echo Spigot "$version" is already installed
   fi