Android: Increment targetSdkVersion to 30 (Android 11)

This enables scoped storage for new Dolphin installs on Android 11
and up (along with a few other changes in behavior which unlike
scoped storage are uncontroversial). Existing installs are unaffected.

We have to do this in order to be able to release updates on
Google Play from November 2021 and on.

Source/Android/app/build.gradle

@@ -25,7 +25,7 @@ android {
         // TODO If this is ever modified, change application_id in strings.xml
         applicationId "org.dolphinemu.dolphinemu"
         minSdkVersion 21
-        targetSdkVersion 29
+        targetSdkVersion 30
 
         versionCode(getBuildVersionCode())
 

Source/Android/app/src/main/AndroidManifest.xml

@@ -35,6 +35,7 @@
         android:label="@string/app_name"
         android:icon="@drawable/ic_launcher"
         android:requestLegacyExternalStorage="true"
+        android:preserveLegacyExternalStorage="true"
         android:allowBackup="false"
         android:supportsRtl="true"
         android:isGame="true"