updating Android NDK version that integration_test requires

Author: Dhanesh-Sawant

android/app/build.gradle

@@ -21,7 +21,7 @@ try {
 
 android {
     namespace "com.zulip.flutter"
-
+    ndkVersion = "26.3.11579264"
     compileSdkVersion flutter.compileSdkVersion
 
     compileOptions {