android: fix warning, set namespace in gradle instead of manifest

Author: igagis

build/android/ruis/build.gradle

@@ -5,6 +5,8 @@ apply plugin: 'com.ydq.android.gradle.native-aar.import' // must go after androi
 android {
     compileSdkVersion 29
 
+    namespace "cppfw.github.io.ruis"
+
     defaultConfig {
         minSdkVersion 21
         targetSdkVersion 29

build/android/ruis/src/main/AndroidManifest.xml

@@ -1,6 +1,4 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-
-    package="cppfw.github.io.ruis">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
 
     <application>