Aperture: Undefine testInstrumentationRunner

Change-Id: I3ddfda8f7711d72dd5857c4f126c910f29e55506
diff --git a/app/build.gradle.kts b/app/build.gradle.kts
index 1f20657..1ad99a5 100644
--- a/app/build.gradle.kts
+++ b/app/build.gradle.kts
@@ -16,8 +16,6 @@
         targetSdk = 33
         versionCode = 1
         versionName = "1.0"
-
-        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }
 
     buildTypes {