fix: update build.gradle to use testRuntimeOnly for JUnit Jupiter engine

app/build.gradle

@@ -19,9 +19,7 @@ repositories {
 dependencies {
     // Use JUnit Jupiter for testing.
     testImplementation 'org.junit.jupiter:junit-jupiter:5.9.1'
-
-    // This dependency is used by the application.
-    implementation 'com.google.guava:guava:31.1-jre'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.9.1'
 }
 
 application {