Remove Multidex usages (#5034)

Since the min SDK is 23, it is no longer necessary to use the Multidex library.

See the following for more info: https://developer.android.com/build/multidex#mdex-on-l

catroid/build.gradle

@@ -125,7 +125,6 @@ android {
         versionName defaultVersionName
         println "VersionCode is $versionCode"
         println "VersionName is $versionName"
-        multiDexEnabled true
         manifestPlaceholders += [appName: manifestAppName,
                                  appIcon: manifestAppIcon,
                                  intentFilterScheme: "https",
@@ -386,7 +385,6 @@ dependencies {
     implementation 'androidx.browser:browser:1.2.0'
 
     implementation "androidx.test.espresso:espresso-idling-resource:$espressoVersion"
-    implementation 'androidx.multidex:multidex:2.0.1'
 
     implementation ('com.opencsv:opencsv:5.0') {
         exclude group: 'org.apache.commons', module: 'commons-text'
@@ -498,7 +496,6 @@ dependencies {
     testImplementation 'org.powermock:powermock-api-mockito2:2.0.0'
 
     testImplementation 'org.robolectric:robolectric:4.7.3'
-    testImplementation 'org.robolectric:shadows-multidex:4.7.3'
 
     testImplementation 'org.reflections:reflections:0.9.11'
     testImplementation 'org.json:json:20190722'

catroid/src/main/java/org/catrobat/catroid/CatroidApplication.java

@@ -40,8 +40,6 @@
 
 import java.util.Locale;
 
-import androidx.multidex.MultiDex;
-
 public class CatroidApplication extends Application {
 
 	private static final String TAG = CatroidApplication.class.getSimpleName();
@@ -89,12 +87,6 @@ private void setupHuaweiMobileServices() {
 		MLApplication.getInstance().setApiKey(apiKey);
 	}
 
-	@Override
-	protected void attachBaseContext(Context base) {
-		super.attachBaseContext(base);
-		MultiDex.install(this);
-	}
-
 	public synchronized Tracker getDefaultTracker() {
 		if (googleTracker == null) {
 			googleTracker = googleAnalytics.newTracker(R.xml.global_tracker);