Support fabric 1.15.10

The club's server is slightly outdated and I couldn't find an easy way to
update it so just changed the required version to allow the mod to work on it.

gradle.properties

@@ -6,7 +6,7 @@ org.gradle.parallel=true
 # check these on https://fabricmc.net/develop
 minecraft_version=1.20.6
 yarn_mappings=1.20.6+build.3
-loader_version=0.15.11
+loader_version=0.15.10
 fabric_kotlin_version=1.11.0+kotlin.2.0.0
 
 # Mod Properties