Bump compileSdk and targetSdk to 30

Signed-off-by: Álvaro Brey Vilas <alvaro.brey@nextcloud.com>

build.gradle

@@ -117,11 +117,11 @@ android {
             'InvalidPeriodicWorkRequestInterval' // crashes due to a bug in lint itself
     }
 
-    compileSdkVersion 29
+    compileSdkVersion 30
 
     defaultConfig {
         minSdkVersion 23
-        targetSdkVersion 29
+        targetSdkVersion 30
 
         // arguments to be passed to functional tests
         testInstrumentationRunner "com.nextcloud.client.ScreenshotTestRunner"