Fix broken reference to a missing resource ID

Seems like a fallout of the change done in PR commons-app#5464

This hopefully should make the instrumentation tests resume.

Author: sivaraam

app/src/androidTest/java/fr/free/nrw/commons/UploadTest.kt

@@ -234,7 +234,7 @@ class UploadTest {
                         .actionOnItemAtPosition<UploadMediaDetailAdapter.ViewHolder>(0,
                                 MyViewAction.typeTextInChildViewWithId(R.id.description_item_edit_text, "Test description")))
 
-        onView(withId(R.id.btn_add_description))
+        onView(withId(R.id.btn_add))
                 .perform(click())
 
         onView(withId(R.id.rv_descriptions)).perform(