fix: fix test compile error

Author: hanlyjiang

lib_fileviewer/build.gradle

@@ -25,7 +25,7 @@ android {
 dependencies {
 // implementation fileTree(include: ['*.jar'], dir: 'libs')
  implementation 'androidx.appcompat:appcompat:1.0.0'
- testImplementation 'junit:junit:4.12'
+ testImplementation 'junit:junit:4.13.2'
  androidTestImplementation('androidx.test.espresso:espresso-core:3.1.0', {
  exclude group: 'com.android.support', module: 'support-annotations'
  })

lib_fileviewer/src/androidTest/java/com/artifex/mupdf/fitz/ExampleInstrumentedTest.java

@@ -2,7 +2,7 @@
 
 import android.content.Context;
 import androidx.test.platform.app.InstrumentationRegistry;
-import androidx.test.ext.junit.runners.AndroidJUnit4;
+import androidx.test.runner.AndroidJUnit4;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -19,7 +19,7 @@ public class ExampleInstrumentedTest {
  @Test
  public void useAppContext() throws Exception {
  // Context of the app under test.
- Context appContext = InstrumentationRegistry.getTargetContext();
+ Context appContext = InstrumentationRegistry.getInstrumentation().getContext();
 
  assertEquals("com.artifex.mupdf.fitz.test", appContext.getPackageName());
  }