Add `libs.testRunner` as it contains missing AndroidJUnitRunner class

TESTED: Generated APK and insepcted the DEX file and it contained
androidx.test.runner.AndroidJUnitRunner, which it didn't before

BUG: 381575705
Change-Id: I5f76ad09ba157ac0f8f75fae9a21d3773b5eed27
diff --git a/app/build.gradle b/app/build.gradle
index f902dac..a1aa73e 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -14,8 +14,6 @@
     compileSdk = 35
 
     defaultConfig {
-        targetSdk = 35
-
         // The schemas directory contains a schema file for each version of the Room database.
         // This is required to enable Room auto migrations.
         room {
@@ -49,6 +47,7 @@
 
     // AndroidX
     implementation(libs.androidx.core)
+    implementation(libs.testRunner)
     implementation("androidx.navigation:navigation-compose:2.8.2")
     implementation("androidx.lifecycle:lifecycle-viewmodel-compose:2.8.4")
     implementation("androidx.palette:palette:1.0.0")