chore: revert changes

Author: MichaelVerdon

packages/firebase_database/firebase_database/android/src/main/kotlin/io/flutter/plugins/firebase/database/TransactionHandler.kt

@@ -25,15 +25,15 @@ class TransactionHandler @JvmOverloads constructor(
 
   @NonNull
   override fun doTransaction(@NonNull currentData: MutableData): Transaction.Result {
-    val snapshotMap = HashMap<String, Any?>().apply {
-      put(Constants.KEY, currentData.key ?: "")
-      put(Constants.VALUE, currentData.value)
-    }
+    val snapshotMap = mapOf(
+      Constants.KEY to (currentData.key ?: ""),
+      Constants.VALUE to currentData.value
+    )
 
-    val transactionArgs = HashMap<String, Any?>().apply {
-      put(Constants.SNAPSHOT, snapshotMap)
-      put(Constants.TRANSACTION_KEY, transactionKey)
-    }
+    val transactionArgs = mapOf(
+      Constants.SNAPSHOT to snapshotMap,
+      Constants.TRANSACTION_KEY to transactionKey
+    )
 
     return try {
       val executor = TransactionExecutor(channel)

packages/firebase_database/firebase_database/example/android/app/build.gradle

@@ -45,7 +45,7 @@ android {
         applicationId = "io.flutter.plugins.firebase.database.example"
         // You can update the following values to match your application needs.
         // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
-        minSdk = 23
+        minSdkVersion flutter.minSdkVersion
         targetSdk = flutter.targetSdkVersion
         versionCode = flutterVersionCode.toInteger()
         versionName = flutterVersionName