jme3-android-examples: upgrade the "junit" library to v4.13.2

jme3-android-examples/build.gradle

@@ -41,7 +41,7 @@ android {
 
 dependencies {
     implementation fileTree(dir: 'libs', include: ['*.jar'])
-    testImplementation 'junit:junit:4.12'
+    testImplementation 'junit:junit:4.13.2'
     implementation 'com.android.support:appcompat-v7:28.0.0'
 
     implementation project(':jme3-core')