Removed unused category view in app details.

It was hidden some time ago, and nobody seems to miss it.
Also, we will be redoing this view soon anyway. In the meantime,
this category stuff is changing and this view should be removed.

app/src/main/java/org/fdroid/fdroid/AppDetails.java

@@ -1307,14 +1307,6 @@ public class AppDetails extends AppCompatActivity {
                 tv.setVisibility(View.GONE);
             }
 
-            // Categories TextView
-            final TextView categories = (TextView) view.findViewById(R.id.categories);
-            if (prefs.expertMode() && app.categories != null) {
-                categories.setText(TextUtils.join(", ", app.categories));
-            } else {
-                categories.setVisibility(View.GONE);
-            }
-
             Apk curApk = null;
             for (int i = 0; i < appDetails.getApks().getCount(); i++) {
                 final Apk apk = appDetails.getApks().getItem(i);

app/src/main/res/layout/app_details_summary.xml

@@ -48,15 +48,6 @@
         android:layout_height="wrap_content"
         android:textSize="12sp" />
 
-    <!-- android:visibility="gone" because not needed in app details imho (but maybe will get used in another place soon) -->
-    <TextView
-        android:id="@+id/categories"
-        android:layout_width="fill_parent"
-        android:layout_height="wrap_content"
-        android:textSize="12sp"
-        android:visibility="gone"
-        tools:text="System" />
-
     <TextView
         android:id="@+id/antifeatures"
         android:layout_width="fill_parent"