conf: Upgrade compileSdkVersion and kotlin_version.

Author: BURG3R5

android/app/build.gradle

@@ -26,7 +26,7 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 31
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8

android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.6.10'
     repositories {
         google()
         mavenCentral()