remove "Debug Calls"

src/main/java/org/thoughtcrime/securesms/ConversationActivity.java

@@ -534,8 +534,7 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
 
     menu.findItem(R.id.menu_start_call)
         .setVisible(
-            Prefs.isCallsEnabled(this)
-                && Build.VERSION.SDK_INT >= Build.VERSION_CODES.O
+            Build.VERSION.SDK_INT >= Build.VERSION_CODES.O
                 && dcChat.canSend()
                 && dcChat.isEncrypted()
                 && !dcChat.isSelfTalk()

src/main/java/org/thoughtcrime/securesms/preferences/AdvancedPreferenceFragment.java

@@ -187,24 +187,6 @@ public class AdvancedPreferenceFragment extends ListSummaryPreferenceFragment
           });
     }
 
-    Preference callsEnabled = this.findPreference("pref_calls_enabled");
-    if (callsEnabled != null) {
-      callsEnabled.setOnPreferenceChangeListener(
-          (preference, newValue) -> {
-            if ((Boolean) newValue) {
-              new AlertDialog.Builder(requireActivity())
-                  .setTitle("Thanks for helping to debug \"Calls\"!")
-                  .setMessage(
-                      "• You can now debug calls using the \"phone\" icon in one-to-one-chats\n\n"
-                          + "• The experiment is about making decentralised calls work and reliable at all, not about options or UI. We're happy about focused feedback at support.delta.chat\n\n")
-                  .setCancelable(false)
-                  .setPositiveButton(R.string.ok, null)
-                  .show();
-            }
-            return true;
-          });
-    }
-
     selfReportingCheckbox = this.findPreference("pref_stats_sending");
     if (selfReportingCheckbox != null) {
       selfReportingCheckbox.setOnPreferenceChangeListener(

src/main/java/org/thoughtcrime/securesms/util/Prefs.java

@@ -202,10 +202,6 @@ public class Prefs {
     return getBooleanPreference(context, "pref_new_broadcast_list", false);
   }
 
-  public static boolean isCallsEnabled(Context context) {
-    return getBooleanPreference(context, "pref_calls_enabled", false);
-  }
-
   // ringtone
 
   public static @NonNull Uri getNotificationRingtone(Context context) {

src/main/res/xml/preferences_advanced.xml

@@ -30,11 +30,6 @@
             android:summary="@string/pref_experimental_features_explain"
             android:selectable="false" />
 
-        <org.thoughtcrime.securesms.components.SwitchPreferenceCompat
-            android:defaultValue="false"
-            android:key="pref_calls_enabled"
-            android:title="Debug Calls" />
-
         <org.thoughtcrime.securesms.components.SwitchPreferenceCompat
             android:defaultValue="false"
             android:key="pref_new_broadcast_list"