fix(core): repair unexpected public jsonModule

Author: Wesley-Young

acidify-core/src/commonMain/kotlin/org/ntqqrev/acidify/internal/json/message/LightAppJsonModule.kt

@@ -2,7 +2,7 @@ package org.ntqqrev.acidify.internal.json.message
 
 import kotlinx.serialization.json.Json
 
-val lightAppJsonModule = Json {
+internal val lightAppJsonModule = Json {
     encodeDefaults = true
     ignoreUnknownKeys = true
 }