Fix JSON instance warning

Full warning:

> Redundant creation of Json format. Creating instances for each usage can be slow.

Author: jkmassel

android/Gutenberg/src/main/java/org/wordpress/gutenberg/model/EditorPreloadList.kt

@@ -107,6 +107,7 @@ data class EditorPreloadList private constructor(
     fun build(formatted: Boolean = false): String {
         val jsonElement = build()
         return if (formatted) {
+            @Suppress("JSON_FORMAT_REDUNDANT") // This is only used in debug builds
             Json { prettyPrint = true }.encodeToString(jsonElement)
         } else {
             Json.encodeToString(jsonElement)