This means that your code could be obfuscated by proguard so any crash analysis systems could give unreadable logs and advises to create and upload a de-obfuscation file. In Android Studio, you can do by enabling minify in build.gradle(app).
You don’t have to worry about this warning. It’s a warning coming from the new Google Play Console. You can solve it by setting your minimum API level to 29.
For more information, check this: New BETA Version of Google Play Console show this warning: [This App Bundle contains Java/Kotlin code] · Issue #1008 · apache/cordova-android · GitHub
Hope, it helps. 