Update gradle plugins

https://docs.flutter.dev/release/breaking-changes/flutter-gradle-plugin-apply

android/app/build.gradle

@@ -1,3 +1,9 @@
+plugins {
+    id "com.android.application"
+    id "kotlin-android"
+    id "dev.flutter.flutter-gradle-plugin"
+}
+
 def localProperties = new Properties()
 def localPropertiesFile = rootProject.file('local.properties')
 if (localPropertiesFile.exists()) {
@@ -6,11 +12,6 @@ if (localPropertiesFile.exists()) {
     }
 }
 
-def flutterRoot = localProperties.getProperty('flutter.sdk')
-if (flutterRoot == null) {
-    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
-}
-
 def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
 if (flutterVersionCode == null) {
     flutterVersionCode = '1'
@@ -21,9 +22,6 @@ if (flutterVersionName == null) {
     flutterVersionName = '1.0'
 }
 
-apply plugin: 'com.android.application'
-apply plugin: 'kotlin-android'
-apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 // Keys for the android play store
 def keystoreProperties = new Properties()
@@ -55,7 +53,7 @@ if (wgerApiKey == null) {
 }
 
 android {
-    compileSdkVersion 33
+    compileSdkVersion 34
     ndkVersion "25.1.8937393"
 
     compileOptions {
@@ -79,7 +77,7 @@ android {
         // Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "de.wger.flutter"
         minSdkVersion 21
-        targetSdkVersion 33
+        targetSdkVersion 34
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
         manifestPlaceholders += [WGER_API_KEY: wgerApiKey]
@@ -108,7 +106,3 @@ android {
 flutter {
     source '../..'
 }
-
-dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
-}