Address breaking changes.

Author: SimY4

build.gradle.kts

@@ -93,8 +93,7 @@ tasks.register("generate") {
   notCompatibleWithConfigurationCache("Pebble classes are not serializable")
 
   doLast {
-    val engine = PebbleEngine.Builder().loader(FileLoader().apply {
-      prefix = "src/main/templates/"
+    val engine = PebbleEngine.Builder().loader(FileLoader("src/main/templates/").apply {
       suffix = ".pebble"
     }).build()
     val themeTemplate = engine.getTemplate("theme")