Update to compile against API 31

build.gradle.kts

@@ -9,7 +9,7 @@ buildscript {
     }
 
     dependencies {
-        classpath(kotlin("gradle-plugin", "1.5.20"))
+        classpath(kotlin("gradle-plugin", "1.5.21"))
         classpath("com.android.tools.build:gradle:7.0.0-beta05")
         classpath("com.google.firebase:firebase-crashlytics-gradle:2.7.1")
         classpath("com.google.android.gms:oss-licenses-plugin:0.10.4")

gradle.properties

@@ -13,7 +13,6 @@ android.databinding.incremental=true
 android.enableJetifier=true
 android.enableR8.fullMode=true
 android.enableResourceOptimizations=false
-android.injected.testOnly=false
 android.useAndroidX=true
 kapt.incremental.apt=true
 org.gradle.jvmargs=-Xmx1536m

mobile/build.gradle.kts

@@ -11,18 +11,18 @@ plugins {
 android {
     val javaVersion = JavaVersion.VERSION_1_8
     val targetSdk = 29
-    buildToolsVersion = "31.0.0-rc5"
+    buildToolsVersion = "31.0.0"
     compileOptions {
         isCoreLibraryDesugaringEnabled = true
         sourceCompatibility = javaVersion
         targetCompatibility = javaVersion
     }
-    compileSdkPreview = "android-S"
+    compileSdk = 31
     kotlinOptions.jvmTarget = javaVersion.toString()
     defaultConfig {
         applicationId = "be.mygod.vpnhotspot"
         minSdk = 21
-        if (targetSdk == 31) targetSdkPreview = "S" else this.targetSdk = targetSdk
+        this.targetSdk = targetSdk
         resourceConfigurations.addAll(arrayOf("it", "ru", "zh-rCN", "zh-rTW"))
         versionCode = 275
         versionName = "2.12.4"