Prune the api version suffix

This is needed for the test plugin, as the bukkit api does not support these versions in the plugin manifest.

Alternatively we could add another gradle property

test-plugin/build.gradle.kts

@@ -5,7 +5,13 @@ dependencies {
 }
 
 tasks.processResources {
-    val apiVersion = rootProject.providers.gradleProperty("mcVersion").get()
+    var apiVersion = rootProject.providers.gradleProperty("mcVersion").get()
+    // Bukkit api versioning does not support suffixed versions
+    val possibleSuffix = apiVersion.indexOf('-')
+    if (possibleSuffix != -1) {
+        apiVersion = apiVersion.substring(0, possibleSuffix);
+    }
+
     val props = mapOf(
         "version" to project.version,
         "apiversion" to "\"$apiVersion\"",