Fixed the package name to conform to standard in the repo

- replaced com.example with github.nisrulz

using_firebase_db/android/app/src/debug/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.using_firebase_db">
+    package="github.nisrulz.using_firebase_db">
     <!-- Flutter needs it to communicate with the running application
          to allow setting breakpoints, to provide hot reload, etc.
     -->

using_firebase_db/android/app/src/main/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.using_firebase_db">
+    package="github.nisrulz.using_firebase_db">
 
     <!-- io.flutter.app.FlutterApplication is an android.app.Application that
          calls FlutterMain.startInitialization(this); in its onCreate method.

using_firebase_db/android/app/src/main/java/github/nisrulz/using_firebase_db/MainActivity.java

@@ -1,4 +1,4 @@
-package com.example.using_firebase_db;
+package github.nisrulz.using_firebase_db;
 
 import android.os.Bundle;
 import io.flutter.app.FlutterActivity;

using_firebase_db/android/app/src/profile/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.using_firebase_db">
+    package="github.nisrulz.using_firebase_db">
     <!-- Flutter needs it to communicate with the running application
          to allow setting breakpoints, to provide hot reload, etc.
     -->